Rebels in nearby towns said that mobile phone service to Zawiyah had been cut off completely and landline service was intermittent, making it difficult to gather new information about the state of the siege. Second-hand reports through rebel networks on Sunday indicated Libyan army tanks had once again moved into the center of the town.

An hour before dawn on Sunday, Tripoli also erupted in gunfire, the sounds of machine guns and heavier artillery echoing through the capital. The spark was unclear — there were rumors of a conflict within the armed Qaddafi forces — but soon Qaddafi supporters were riding through the streets waving 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, pointing out that 6 a.m. Sunday is an unusual time for a victory rally and that rally was notably well-armed. Protesters in the capital suggested it was a show of force intended to deter unrest or possibly cover up some earlier conflict.A rebel spokesman, reached over the phone, said his leadership was relying on international media reports to try to make sense of the early morning gunfire in Tripoli.

“It is very hard to reach Trip, ” he said, alluding to the pervasive surveillance and recent spate of arrests. “When we talk to someone in Tripoli you put their life in jeopardy.”

By early afternoon Sunday, Libyan state television and government officials in Tripoli were making increasingly strong and apparently false statements about progress against the rebels. Officials said that Qaddafi forces had captured the city of Misrata as well as the leaders of the rebels governing counsel and would soon retake the country. State television reported that Qaddafi forces were marching on the rebel headquarters of Benghazi. But multiple reports from the ground on the front lines and in rebel territory indicated that all those reports were false and in fact rebels were fighting near the port of Surt, the town where Colonel Qaddafi was born and which blocks the rebels’ progress toward Tripoli.

Rebels in control of Misrata said they had successfully rebuffed a Libyan army incursion into their town. One witness said their forces had surrounded a contingent of Libyan army trucks and personnel carriers after it entered the town in a battle that killed as many as nine Libyan soldiers and four rebels.

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.”

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.

Source: http://www.nytimes.com