KENNEDY SPACE CENTER, Fla. — The shuttle Discovery braved the hellish fire of re-entry for the last time Wednesday and glided back to Earth to close out the space plane’s 39th and final voyage, an emotion-charged milestone marking the beginning of the end for America’s shuttle program.       

Dropping through a partly cloudy sky, the commander, Steven W. Lindsey, and Col. Eric A. Boe of the Air Force guided Discovery through a sweeping left overhead turn, lined up on Runway 15 and floated to a picture-perfect touchdown at 11:57 a.m. Eastern time to wrap up an extended 13-day space station assembly mission.       

As it coasted to a stop under a brilliant noon sun, Discovery’s odometer stood at some 5,750 orbits covering nearly 150 million miles during 39 flights spanning a full year in space — a record unrivaled in the history of manned rockets.       

“And Houston, Discovery, for the final time, wheels stopped,” Mr. Lindsey radioed flight controllers in Houston.       

“Discovery, Houston, great job by you and your crew,” replied Charles Hobaugh, an astronaut in mission control. “That was a great landing in tough conditions, and it was an awesome docked mission you all had.”       

Mr. Lindsey and Colonel Boe were joined aboard Discovery by Capt. Benjamin Alvin Drew Jr. of the Air Force; Nicole P. Stott; Michael R. Barratt, a physician-astronaut; and Capt. Stephen G. Bowen of the Navy.       

As support crews swarmed onto the broad runway, engineers in the nearby Vehicle Assembly Building were busy preparing the shuttle Endeavour for rollout. The target date for Endeavour’s 25th and final flight is April 19.       

NASA’s lone remaining orbiter, the Atlantis, is scheduled for liftoff June 28 on the shuttle program’s 135th flight, the final chapter in a post-Apollo initiative that produced what is arguably the most complex, capable and costly manned rockets ever built.       

”We’re seeing a program come to a close here, and to see these shuttles, these beautiful, magnificent flying machines, end their service life is obviously a little bit sad for us,” said Dr. Barratt.       

“But it is about time — they’ve lived a very long time, they’ve had a fabulous success record,” he added. “We look forward to seeing them retire with dignity and bringing on the next line of spaceships.”       

What sort of spaceship might ultimately replace the shuttle is an open question, and it is not yet clear how NASA will fare in the ongoing budget debate.       

But between Atlantis’ landing this summer and the debut of whatever vehicle replaces it — several years from now at best — the only way for American astronauts to reach orbit will be to hitch rides aboard Russian Soyuz spacecraft at $55 million a seat.       

That is a bitter pill for the thousands of men and women who have worked on the shuttle fleet over the past three decades, who now face layoffs and the prospect of seeing Discovery, Endeavour and Atlantis — the world’s most sophisticated spacecraft — turned into museum displays.       

“We won’t do anything nearly as complex with another vehicle for a very long time,” Captain Drew said. “Five or 10 years from now, they’re going to look back and say ‘How did we ever build a vehicle that could do all these things?’ ”       

BREGA, Libya — Forces loyal to the Libyan leader, Col. Muammar el-Qaddafi, repulsed a rebel push to the west on Wednesday and then counterattacked with airstrikes and increasingly accurate artillery fire on the strategic refinery town of Ras Lanuf, which the rebels have held for several days.       

In the western half of the country, elite government troops continued to pound the besieged, rebel-held city of Zawiyah, only 30 miles from Colonel Qaddafi’s stronghold, the capital city of Tripoli. The government claimed to have mostly recaptured Zawiyah on Wednesday, but it has made such claims falsely in the past.       

However, rebels in the city reported being pinned down by tank and sniper fire, and clinging to the city’s central Martyrs’ Square as they made their last stand against government troops, Reuters reported.       

By late afternoon, state television was broadcasting scenes of wild celebration in the square by Qaddafi loyalists waving green flags. But there was no way to verify the report, and a state-sponsored reporting trip to the city for foreign journalists was abruptly canceled.       

Opposition leaders in the city told Reuters that the setback was only temporary, and that they would regain control during the night.       

In Ras Lanuf, witnesses reported seeing warplanes circling the refinery in the early afternoon, followed by an explosion and thick plumes of black smoke. The blast did not seem to come from the heart of the facility, the witnesses said, but off to the side in an area of numerous large storage tanks.       

A rebel spokesman told The Associated Press that Qaddafi’s forces had hit a pipeline carrying crude oil to the refinery, while the government blamed the blast on rebel forces allied with Al Qaeda. An official with Libya Emirate Oil Refining Company said the plant had been closed down, not from damage but because most of the employees had fled.       

The rebels, reinforced on Tuesday by dozens of trucks with heavy weapons and cadres of professional soldiers, made a move west toward the town of Bin Jawwad, having been driven from there days ago, blunting their efforts to continue a march toward Tripoli. On Wednesday, during the onslaught, hundreds of rebel fighters had advanced more than a half mile to the west.       

As Colonel Qaddafi’s forces try to retake a series of strategic oil towns on the east coast of the country, which fell early in the rebellion to antigovernment rebels, the West continues to debate what actions to take, including the creation of a possible no-flight zone to ground Libyan warplanes.       

On Wednesday, speaking in an interview with Turkish public television, Colonel Qaddafi vowed that his countrymen would take up arms to resist such measures, calling them an attempt to rob Libyans of their freedom and their oil.       

The debate on a no-flight zone has become louder in world capitals. European countries like Britain and France seem to favor the idea while the United State defense secretary, Robert M. Gates, has underscored the difficulties of imposing such a ban, though he has seemed to soften his resistance in recent days. Britain and France are working on a United Nations resolution to authorize a no-flight zone, although it was unclear whether such a measure could gain the necessary votes of Russia and China in the Security Council.       

President Obama and the British prime minister, David Cameron, in a phone call Tuesday, agreed on the shared objective of “the departure of Qaddafi from power as quickly as possible,” the White House said in a statement, adding that they would “press forward with planning, including at NATO, on the full spectrum of possible responses, including surveillance, humanitarian assistance, enforcement of the arms embargo and a no-fly zone.”       

Human rights abuses by the Qaddafi government could provide another possible trigger for international intervention, and on Wednesday the United Nations special rapporteur for torture, Juan E. Méndez, said that his agency was investigating a series of opposition charges of atrocities in the days before Feb. 25, when the government invited foreign journalists into Tripoli to report on the uprising, The Associated Press reported. The accusations include picking up the wounded off city streets and using ambulances to gain admission to hospitals and then taking away patients, who were subsequently tortured and, in some cases, executed.       

Envoys for Colonel Qaddafi fanned out across Europe and, according to some reports, Latin America and Africa, for purposes that remained obscure. Emissaries were reported to have visited Egypt, Greece, Portugal, Malta and Brussels in an effort to head off international action against Libya, and Greece confirmed that the Colonel himself had spoken with the Greek prime minister, George A. Papandreou. An analyst with contacts in the Libyan iuntelligence services, told Reuters that some of the missions, particularly those to Latin American and African countries, might well constitute preliminary discussions about a refuge for the Qaddafis should they be forced to flee. But that report could not be confirmed.       

Egyptian officials, who spoke in return for anonymity under departmental rules, said Colonel Qaddafi sent an emissary to Cairo on Wednesday. A Libyan jet landed in the Egyptian capital, the officials said. carrying a senior military official — Maj. Gen. Abdel Rahman Ben Ali, identified as the deputy minister of Libya’s logistics and supply ministry. Security officials said he was received by Egyptian military intelligence.       

The nature of the visit was unclear, though reports have emerged in recent days of a major effort by Islamic agencies to supply the rebel-held east with food, medical supplies and other humanitarian aid. Cairo also hosts the Arab League, which is set to debate the issue of a no-flight zone this weekend, news reports said. Libya’s representative at the Arab League resigned last month, saying the Libyan leader had lost all legitimacy.       

The plane, a private Falcon jet, took off from a small Libyan airfield and flew through Maltese and Greek airspace, news reports said. Since Libya’s uprising began last month, Colonel Qaddafi has seemed isolated with few, if any, Arab leaders ready to speak to him, publicly at least. The officials said General Ben Ali was seeking a meeting with the military council running Egypt since last month’s ouster of President Hosni Mubarak.       

But Musa Ibrahim, a spokesman for Colonel Qaddafi, said there would be nothing unusual about the flight since Libya was in constant touch with its neighbors about the crisis in the region. Speaking to reporters, he did not comment on the specific flight on Wednesday. Despite Libya’s turmoil, commercial flights from Tripoli are still flying to cities in the region and elsewhere. There was no indication of whom General Ben Ali intended to see.       

Two planeloads of Libyan officials were also en route to Brussels on Wednesday to confer with European Union and NATO officials, Al Jazeera reported, to argue against the imposition of a no-flight zone and other measures against Libya.       

In his interview with Turkish journalists in Tripoli, broadcast in Turkey on Wednesday, Colonel Qaddafi seemed almost to welcome the idea of a no-flight zone himself, arguing that it would expose Western motives.       

“Such a move would be very useful in a way that all Libyan people would then realize that their real intention is to take Libya under control, take people’s freedoms away and seize their oil,” he said. “Therefore, all Libyan people would take up arms and fight.”       

As on several occasions in the past, he argued that Libya has provided a guarantee of security in the Mediterranean stretching to southern Europe, standing as a bulwark against Al Qaeda.       

“The stability of Libya means the security of the Mediterranean and therefore the security of the world,” Colonel Qaddafi said. “If Al Qaeda takes over in Libya, it would be a major disaster and Europe would soon be filled with refugees that Al Qaeda would transfer from Africa.”       

“If they seize control here, the whole region including Israel would be dragged into chaos,” he said. “No one can prevent them as efficiently as we did.”       

Global powers seem frustrated by their apparent inability to influence events here, with Colonel Qaddafi seemingly impervious to criticism and rebels in eastern Libya cautious about accepting Western help beyond the imposition of a no-flight zone.       

The diplomatic and political effort to force Colonel Qaddafi’s departure is focused on NATO meetings in Brussels on Thursday and Friday.       

The Pentagon press secretary, Geoffrey Morrell, told reporters traveling with Mr. Gates from Afghanistan to Brussels on Wednesday that the defense secretary’s position on a possible no-flight zone had not changed — in short, that it remains one of a number of potential military courses of action that Mr. Gates is providing to Mr. Obama.       

“We are committed to providing the president with the full range of options for him to consider, including a no-fly zone,” Mr. Morrell said on Mr. Gates’ plane. “But he also sees it as his responsibility to provide the president and his national security team with the potential consequences of military action. So that work has been and is underway.”       

Mr. Morrell took issue with suggestions that Mr. Gates, based on comments the defense secretary made on Capitol Hill last week, was adamantly opposed to a no-flight zone. In those comments, Mr. Gates said that people should “call a spade a spade” and recognize that establishing a no-flight zone would first require strikes on Libya’s air defense system.       

In previous public statement, Mr. Gates has said that now is not the time for the United States to get involved in another war in the Middle East.       

Despite those remarks, Mr. Morrell said that Mr. Gates “has not staked out a position in opposition to any particular course of action.”       

In the Middle East, the Gulf Cooperation Council has already endorsed a no-flight zone, and speaking in Washington, a representative of the Arab League said it was expected to support the idea as well. Western leaders have stressed the need for international support before undertaking a no-flight zone, so they do not appear to be meddling.       

A report released Tuesday by the International Institute for Strategic Studies, a London-based group known for its assessments of relative military strength, underscored the challenge facing the rebels. Colonel Qaddafi “has long neglected the military formations in the east; the dilapidated bases and installations there contrast sharply with the well-kept barracks and tank parks outside Tripoli,” the report said, relying in part on satellite images to compare the number and make of tanks and other equipment. “This goes a long way toward explaining why the momentum generated by the revolution has yet to overwhelm pro-regime forces.”       

Air power is Colonel Qaddafi’s biggest advantage, the report found, noting that so far the rebels appeared unable to use bases and planes they captured in the east. Planes and helicopters give the Qaddafi forces an additional advantage, the report said, in moving ammunition and supplies, a crucial factor given the length of the Libyan coast between the rebel stronghold of Benghazi and Tripoli.       

LOS ANGELES — Since getting sober more than two decades ago, Tom Arnold, the actor and comedian, has been a quiet force in Hollywood’s recovery community, helping stage a number of interventions for drug-addicted executives and alcoholic stars.       

But even a seen-it-all show business survivor like Mr. Arnold was stunned by what happened when he tried to pull his friend and former neighbor, Charlie Sheen, back from the brink.       

“I went to a person close to him and said, ‘This guy is in serious trouble with serious drugs. We’ve got to help him,’ ” Mr. Arnold recalled in an interview. “And this person flat-out told me to my face, ‘We make a lot of money from him. I can’t be part of it.’ That tells you everything you need to know.”       

While bad behavior by star performers is tolerated in a number of industries — sports and high fashion, for example — Hollywood has a longer public history of aiding and abetting addicts. Doctors employed by Metro-Goldwyn-Mayer famously gave Judy Garland amphetamines and other drugs to combat fatigue and control her weight, setting up a life-long battle with drug addiction that she ultimately lost.       

“One of the problems with the entertainment industry is that, to protect the image of these people, they try to deal with the problem by sweeping it under the rug,” said John T. Schwarzlose, chief executive of the Betty Ford Center, the licensed addiction hospital in Rancho Mirage, Calif.       

In the case of a crack-smoking, prostitute-frequenting Mr. Sheen, many people in Hollywood say there is a long list of enablers: managers and agents and publicists; a coterie of assistants and party buddies; prostitutes, drug dealers and sex film stars; and the tabloid media, which have fed on Mr. Sheen’s antics for years.       

Their efforts may have sustained Mr. Sheen during his long career, but they seem to have finally backfired. As the lead actor of a No. 1-rated sitcom, Mr. Sheen is that rare commodity in today’s Hollywood — a bankable and irreplaceable star — and his public crackup has come at perhaps the most valuable point in his career.       

CBS, which broadcasts “Two and a Half Men,” and Warner Brothers, which makes it, have shut down the remainder of this season and could lose more than $250 million in revenue if next season is lost as well.       

That decision was made only after what executives from the two companies described as years of efforts to try to convince Mr. Sheen to concede he had serious addiction problems.       

“There is a long history here,” one senior executive involved in the supervision of the program said. The executive asked not to be identified because of the potential legal conflict looming between the network and the studio and Mr. Sheen. (Mr. Sheen, who has talked to just about everybody else in the past week, did not respond to requests to comment for this article.)       

The senior executive described a recent trip to Mr. Sheen’s home by the top executive at CBS, Leslie Moonves, and the head of the Warner television group, Bruce Rosenblum.       

They reported that Mr. Sheen had looked haggard and nothing like the leading man of a hit show. They said that Mr. Sheen had agreed to enter a rehabilitation facility, but when he decided a few days later that he would conduct his own rehab work at home, they concluded that “Charlie had thumbed his nose” at them.       

It was not the first time that the show’s managers had tried to intercede, but they had limited options: Mr. Sheen’s contract does not include any kind of morals provision that would have allowed him to be fired or replaced. According to one longtime Hollywood agent (who, like many people quoted in this article, spoke on the condition of anonymity so as not to create any conflicts in their business), the show’s success had provided him with the leverage he needed to keep any such clause out.       

“He’s money,” this agent said. “He makes the cash register ring.”       

Many of the people in the best position to discuss Mr. Sheen’s drug abuse over the years declined to speak. His father, Martin Sheen, is out of the country, according to a spokesman; Charlie Sheen’s managers, Mark Burg and Oren Koules of Evolution Entertainment, did not respond to multiple interview requests. A spokeswoman for Mr. Sheen’s brother, Emilio Estevez, was similarly unresponsive. Oliver Stone, who directed the young Mr. Sheen in two seminal movies, “Platoon” and “Wall Street,” declined to comment.       

A person who was closely associated with Mr. Sheen in the 1990s said the actor’s sheer stamina allowed him to mix work and play in ways that would surely have immobilized others.       

“He does show up,” this person said of Mr. Sheen’s work habits. “He might be out until 5 a.m., but he always showed up on call at 7.”       

But it was not just Mr. Sheen’s iron constitution that allowed him to keep working. Ask people who have worked with him what they remember about him and the answer almost always involves generosity on the set and an almost otherworldly degree of likability despite his demons.       

Jim Abrahams, who directed Mr. Sheen in two comedies from the early 1990s, “Hot Shots!” and “Hot Shots! Part Deux!,” remembered how Mr. Sheen, learning that the director was a sports fan and from Wisconsin, bought memorabilia for him as thank you gifts, including a signed 1957 Milwaukee Braves baseball.       

“He is a profoundly talented actor,” said Mr. Abrahams, whose résumé also includes the screenplay for “Airplane.” “I don’t recognize the bitter and angry guy who has been doing these television interviews. I just never saw any of that, and it wasn’t like he wasn’t getting loaded in his private time back then.”       

Indeed, Mr. Abrahams said Mr. Sheen was quite open about his drug abuse at the time, even opening up about the toll it had already taken on his mind. “He told me that he would look at movies he had done and not remember having done entire scenes — not because he was under the influence while acting, but because the partying had started to take a toll on his overall memory.”       

Penelope Spheeris, who directed Mr. Sheen in the 1985 film “The Boys Next Door,” recalled a business meeting in the early 1990s about a potential movie. “Charlie wasn’t in the best shape — a little woozy,” she said, adding, “But you have to remember what this business is like. I’ve been in a lot of meetings with loaded people.”       

Mr. Sheen’s movie paydays peaked with Disney’s “Terminal Velocity,” a 1994 action thriller for which the actor was paid $6 million. The film performed only modestly at the box-office, but the more serious blow to his bankability was almost certainly the public spectacle of his testimony in the federal conspiracy and tax evasion prosecution of Heidi Fleiss, the Hollywood madam.       

In videotaped testimony, Mr. Sheen acknowledged having spent more than $50,000 on prostitutes in a single year. He looked uncomfortable during the testimony, pausing only occasionally to toss in one of the macho zingers that would be his trademark on “Two and a Half Men.”       

“Heterosexual services,” he said at one point, clarifying what Ms. Fleiss had provided. Confronted with the checks he had written to her, he said: “Sheesh, it’s starting to add up.”       

He has also been involved in domestic violence incidents with two of his wives, and last fall, a hired escort claimed he had put his hands around her throat.       

Some in the industry said his behavior toward women was tolerated because, at some level, Hollywood retains a boys’ club atmosphere, and companies could point to the fact that he was either not charged or received light penalties in the incidents.       

There have been other people in Mr. Sheen’s life aside from Mr. Arnold who have been trying to get the star into treatment. Mr. Sheen has said in interviews that people like Sean Penn and Mel Gibson, along with some of his lesser-known actor friends, have tried to intervene.       

Martin Sheen, who struggled with addiction in the past, has perhaps pushed the hardest. In 1998, when Charlie Sheen was taken by ambulance to a hospital for “extreme exhaustion,” his father held a tearful news conference. “My son had a drug overdose,” he said. “It is our hope that he will accept recovery and finally be free.”       

Charlie Sheen eventually did go to rehab, but the incident caused a rift.       

“That’s a big no-no — saying what actually happened,” Mr. Arnold said. “Charlie was mad about it. He didn’t speak to his dad for a while after that. But it saved Charlie’s life at the time, I’m sure of it.”       

In 2000, Mr. Sheen largely moved from feature films to television, first as Michael J. Fox’s replacement on “Spin City,” then to “Two and a Half Men” beginning in 2003. In some ways, his current role appears to have been tailored around Mr. Sheen’s off-screen problems. He said in a radio interview that set furniture had been re-arranged so he could lean on something for support.       

The current conflict escalated after Mr. Sheen began speaking out against Chuck Lorre, the show’s creator and a reliable hitmaker for CBS. As he was criticizing Mr. Lorre, Mr. Sheen was railing against the organization Alcoholics Anonymous. The senior executives said the two issues were linked because of Mr. Lorre’s long advocacy of A.A.       

“There had been stress for quite awhile between Charlie and Chuck,” the senior executive said. “The attacks on A.A. were code for Chuck.” (Mr. Lorre declined requests for comment.)       

But despite his recent behavior and his attacks on Mr. Lorre and CBS, not everyone in Hollywood is convinced that Mr. Sheen is off the deep end, even now.       

“I saw him a week ago,” said Mike Medavoy, a film producer who made several films with Mr. Sheen. “He was calm and funny, as usual — it’s always like he wants to be the class clown.”       

Mr. Medavoy said Mr. Sheen had been a “consummate professional” when making films. “Once the media gets hold of a story, it becomes a decision for the people to figure out whether he’s really crazy,” Mr. Medavoy said. “The truth of the matter is, he could be crazy like a fox.”       

TRIPOLI, Libya — Both sides of the conflict in Libya were girding for more confrontations on Sunday, a day after militia forces loyal to Col. Muammar el-Qaddafi launched a new round of attacks on the rebel-held city of Zawiyah, just 30 miles west of the capital, and a ragtag rebel army moving from the east won its first ground battle to take the oil port of Ras Lanuf, about midway down the Mediterranean coast.       

An hour before dawn on Sunday, Tripoli erupted in gunfire, the sounds of machine guns and heavier artillery echoing through the capital. The spark was unclear – — there were rumors of some conflict within the armed Qaddafi forces — but soon Qaddafi supporters were riding through the streets waiving green flags and firing guns into the air. Crowds converged on the city’s central Green Square for a rally, with many people still shooting skyward. The shots rang out for more than three hours, with occasional ambulance sirens squealing in the background.       

Government spokesmen called it a celebration of victories over the rebels, but the rebels denied any losses; 6:00 a.m. Sunday morning is an unusual time for a victory rally, and the rally was notably well armed. Protesters in the capitol suggested it was a show of force intended to deter unrest or possibly cover up some earlier conflict.Both sides were anticipating a showdown in the coming days at the port of Surt, the town where Colonel Qaddafi was born and which blocks the rebels’ progress toward Tripoli.       

Nineteen days after it began with spirited demonstrations in the eastern city of Benghazi, the Libyan uprising has veered sharply from the pattern of relatively quick and nonviolent upheavals that ousted the leaders of Tunisia and Egypt. Instead, the rebellion here has become mired in a drawn-out ground campaign between two relatively unprofessional and loosely organized forces — the Libyan Army and the rebels — that is exacting high civilian casualties and appears likely to drag on for some time.       

That bloody standoff was evident on Saturday in Zawiyah, the northwestern city seized by rebels a week ago, where the government’s attacks raised puzzling questions about its strategy. For the second day in a row its forces punched into the city, then pulled back to maintain a siege from the perimeter. Hours later, they advanced and retreated again.       

By the end of the day, both sides claimed control of the city.       

Foreign journalists were unable to cross military checkpoints to evaluate reports of what Zawiyah residents called “a massacre.”       

Witnesses there began frantic calls to journalists in Tripoli at 6 a.m. Saturday to report that soldiers of the Khamis brigade, which is named for the Qaddafi son who commands it and is considered the family’s most formidable force, had broken through the east and west gates of the city. “They are killing us,” one resident said. “They are firing on us.”       

The militia attacked with tanks, heavy artillery and machine guns, witnesses said, and the explosions were clearly audible in the background.       

The rebels, including former members of the Libyan military, returned fire. Although a death toll was impossible to determine, one resident said four of his neighbors were killed, including one who was found stripped of his clothes.       

A correspondent for Sky News, a British satellite TV channel and the only foreign news organization in the city, reported seeing the militia fire on ambulances trying to remove the wounded from the streets. The reporter also said she had seen at least eight dead soldiers and five armored vehicles burning in the central square.       

At 10 a.m., witnesses said, the Qaddafi forces abruptly withdrew, taking up positions in a close circle around the city.       

Some rebels painted the pullout as a victory, but others acknowledged that there was little evidence that they had inflicted enough damage on the militia to force the retreat.       

Around 4 p.m., the militia attacked again. A witness said as many as six tanks rolled through town, there were more skirmishes with the rebels, and then the tanks left as quickly as they had arrived.       

At a news conference Saturday night in Tripoli, Deputy Foreign Minister Khalid Kaim described Zawiyah as “peaceful for the moment.” Another foreign ministry official, Yousef Shakir, called it “99 percent” under government control.       

Officials also showed videos that they said proved their opponents were not peaceful demonstrators. Aerial video of Zawiyah showed tanks on the streets and antiaircraft guns on the roofs of mosques.       

Another video was said to show rebel interrogations and executions, which the officials likened to the tactics of Al Qaeda.       

Despite all the footage of rebel weapons, the officials denied they were fighting a civil war. “There are some people who are acting in contravention of the law, which can happen anywhere,” a spokesman said. Mr. Shakir said: “It is a conspiracy, a very highly organized conspiracy. We will show the foreign hands in the near future.”       

In Benghazi, the rebels’ de facto capital, the rebels took further steps toward political organization. Their shadow government, the Libyan National Council, held its inaugural meeting Saturday and appointed a three-member crisis committee.       

Abdul Hafidh Ghoga, a spokesman for the council, seemed to back away from previous calls by rebel leaders for Western airstrikes, saying emphatically, “No troops on Libyan soil.” But he added that the rebels would welcome the imposition of a no-flight zone, and said, “We require help to stop the flow of mercenaries into this country.”       

While the rebels may have a new defense minister in Benghazi, their fighters on the eastern front did not appear to be taking orders from anyone on Saturday as they pushed past Ras Lanuf, an oil refinery town that they retook from Colonel Qaddafi’s loyalists on Friday night.       

Armed with rocket-propelled grenade launchers, the rebels advanced confidently by car and foot through the desert until a fighter jet was heard. Even a rumor of a jet engine in the distance would send the fighters in a mad dash through the dunes, searching for cover and firing in the air.       

A rebel convoy that encountered an army checkpoint on the road to Surt made a quick U-turn and sped away.       

There did not appear to be much of an air war, although the sounds of fighter jets were heard throughout the day. The convoy was strafed by a helicopter, although no casualties were reported.       

In Ras Lanuf, the bodies of two pilots were found in the wreckage of a Libyan fighter jet, witnesses said. A rebel claim that the jet had been shot down could not be confirmed.       

Rebel military leaders said the explosions at a large ammunition dump on Friday in Benghazi were caused by an airstrike. The explosions leveled at least three buildings, toppled power lines more than 300 yards away and killed at least 16 people.       

There were conflicting reports on casualties in the previous day’s battle for Ras Lanuf. A rebel said that 12 rebels were killed, while hospital officials in the nearby city of Ajdabiya said 5 rebels had been killed and 31 were wounded, The Associated Press reported. Reuters cited doctors saying 26 had died.       

TRIPOLI — A state of terror has seized two working class neighborhoods here that just a week ago exploded in revolt, with residents reporting constant surveillance, heavily armed checkpoints and disappearances of those involved in last week’s protest.       

While rebel fighters in the country’s east celebrated their defeat of an incursion on Wednesday by hundreds of Col. Muammar el-Qaddafi’s loyalists in the strategic oil town of Brega — and fended off a number of airstrikes on Thursday in industrial areas and around the airport, one resident said — many people here in Tripoli were lying low in an effort to elude the secret police.       

Several people in the neighborhoods, Feshloom and Tajura, speaking on condition of anonymity for fear of the secret police, said militias loyal to Colonel Muammar el-Qaddafi are using photographs taken at last week’s protest to track down the young men involved. “They know that there are people who have energy and who are willing to die so they pick them up,” one resident said.       

The resident showed reporters cell phone photographs taken at Tripoli Central Hospital of a large wound in the chest of his family member, Nagi Ali el-Nafishi, 56, and they pointed out the blood stain on the cement where he had been shot almost immediately after leaving Friday prayers at a mosque. A doctor who examined him said that the bullet had exploded his heart and lungs, causing him to die of lost blood within minutes.       

Several people said at least four people in the neighborhood had been killed that day, including Hisham el-Trabelsi, 19, who they said was shot in the head, and Abdel Basit Ismail, 25, hit by random gunfire while she was calling to a family member in the protest. Neighbors in the Feshloom area report discovering the body near the Abu Slim prison of at least one man, Salem Bashir al-Osta, a 37-year-old teacher who disappeared at a protest last Sunday.       

“I think now the people know that if they make any protest now they will be killed, so all the people in Tripoli are waiting for someone to help them from Benghazi,” the neighbor continued, referring to the city in eastern Libya that where the revolt first began and has established a headquarters.       

The Libyan government, meanwhile, accepted a proposal by Venezuela’s President Hugo Chavez, an ally of Colonel Qaddafi, to form an international commission to negotiate a solution to the crisis, a spokesman for the Venezuelan government said. But the proposal was rejected out of hand by rebel leaders, who said too much blood has already been spilled.       

“Nobody approached us,” said Iman Bugaighis, a spokeswoman for the rebel’s interim authority in Benghazi, speaking of Mr. Chavez’s offer. “Nobody is ready for any negotiations. It’s too late. If he wants to leave, fine.”       

Flush with their victory in Brega, rebel fighters had pushed 25 miles to the west on Thursday and established a makeshift checkpoint, where a dozen lightly-armed men stood sentry. They greeted trucks filled with Egyptian men driving east, fleeing Libya for home. Many of the Egyptians said that Colonel Qaddafi’s soldiers had robbed them, taking their cellphones and their money. The rebels gave them juice and water.       

The Pentagon announced on Thursday that it has seen clear evidence that the Qaddafi government has used air power in the conflict, though it is not clear that it is using warplanes to attack protesters — a step that could induce Western powers to establish a no-fly zone. A son of Colonel Qaddafi, Saif al-Islam, said in an interview with Sky News on Thursday that airstrikes in Brega on Wednesday were intended to scare the rebels, “to frighten them to go away, not to kill them.”       

In The Hague, the prosecutor of the International Criminal Court, Luis Moreno-Ocampo, said that Colonel Gaddafi and members of his inner circle, including some of his sons, could be investigated for crimes against humanity committed since the uprising broke out in mid-February.       

A spokesman for the Libyan government, Musa Ibrahim, dismissed the statement from the court, telling Reuters: “No fact-finding mission has been sent to Libya. No diplomats, no ministers, no N.G.O.s or organizations of any type were sent to Libya to check the facts.”       

Residents of Feshloom and Tajura, however, seemed to be awash in evidence of human rights violations, if fearful of passing it on. On Thursday and on several occasions earlier this week, residents pointed to buildings where they say Qaddafi militias have set up local operating bases. They say their streets are pocked with heavily armed checkpoints where the police inspect cars, documents and mobile phones for any signs of participation in the unrest. And on Feshloom on Thursday several said they were afraid to be seen near a foreign journalist.       

“His spies are everywhere! There is somebody watching you right now!” said a man sitting on a store stoop in Feshloom, echoing a sentiment heard from more than half a dozen others. “Many people have been killed here,” he continued, “and if I speak to you, they will come for me.”       

The climate of fear suggests just how effectively Col. Qaddafi’s ruthless application of force in Tripoli has locked down the city, even as the rebels elsewhere have held control of the eastern half of the country as well as a string of smaller western cities surrounding the capital.       

Just days ago a young rebel organizer in Tajura boldly vowed to reporters that his neighborhood would turn out another major protest after this Friday’s prayers. But since then he has been unreachable by telephone or email, and residents of both neighborhoods said they no longer held out much hope for nonviolent demonstrations as a means to dislodge Colonel Qaddafi.       

“If there were weapons, we have good young men who can fight, who can do anything,” one father said with resignation. “But there are no weapons.”       

Colonel Qaddafi’s firm grip on Tripoli — where his government can still easily produce at a moment’s notice a crowd of young men with green flags and bandanas cheering his name and punching their fists — augurs a prolonged standoff with the rebels. Their main front line remains several hundred miles from here, and the rebels in the western cities say that while they control their towns they remain deeply worried about the heavy concentration of tanks and other military forces ringing their perimeters.       

The Libyan leader’s deadly tactics also suggest just how difficult the animosities stirred up by the revolt may be to bury when it is resolved. In a country still bound together by intertwined tribal ties, where large extended families make everyone’s business widely known, rebels say they fear for their lives if their revolt is crushed, and that they know members of Colonel Qaddafi’s security forces must feel the same. One Feshloom resident who lost a family member in the protests said the man’s mother had told him: “I would like to see the Qaddafis killed one by one, and the sons killed first so that he could feel the pain I have felt.”       

Residents of the neighborhoods of Tajura and Feshloom say they have become hotspots of unrest in part because they remain dominated by large clans of people who have lived there for decades, lending a level of trust and cohesion that is absent in areas where Qaddafi loyalists from his home region near Surt and other newcomers have settled in since he came to power 41 years ago.       

And in both neighborhoods residents say disappearances have continued all week as the security forces appear to be rounding up suspected protesters in anticipation of Friday prayers, the customary time for street protests across the Arab world. On Thursday night, a resident of the Tajura neighborhood called a journalist to report five people had been arrested leaving a mosque after dawn prayers on Saturday, including Mohammed Safi, the director of mechanical engineering at a university here. “Every day they take people away. We would like to know where they are, what happened to them?”       

Others said a growing sense of fatalism had set in after the burst of hope a week before. One young man in an upscale café said that with the Benghazi rebels so far off — and so ill-equipped for a siege of the capital — he was hoping for a palace coup. “The people around Qaddafi — that is our only hope,” he said.