Rebels battling the regime of Moammar Gaddafi would accept a cease-fire if government forces pull out of cities they are besieging and allow peaceful protests, the head of the opposition’s interim government said Friday.

On the other side of the strife-torn country, heavy gunfire erupted in the capital, Tripoli, before dawn Friday as tensions rose following rumors that other government officials were preparing to join Musa Kusa, Gaddafi’s foreign minister and former intelligence chief, in defecting from the regime.

Sustained bursts of automatic weapons fire were heard coming from the direction of Gaddafi’s Bab al-Aziziya compound at around 2 a.m. and again shortly before dawn. Ambulances and police cars were seen speeding through the deserted streets, but there was no immediate explanation for the unusual overnight activity.

Gaddafi’s forces, meanwhile, continued to lay siege to Misurata, Libya’s third-largest city 130 miles east of Tripoli, while also pressing an offensive in eastern Libya that has driven the rebels out of several Mediterranean coastal towns and oil hubs this week.

In Misurata, where rebels have been under siege for more than a month, government forces shelled the city with tanks and mortars Friday and attacked shops and homes in the city center, news agencies reported.

About 100 miles south of Benghazi, the anti-Gaddafi forces’ de facto capital in eastern Libya, rebels were guarding the western entrance to the strategic city of Ajdabiya as fighting reportedly continued around Brega, an oil refinery town about 50 miles to the southwest.

“We are seeking immediate withdrawal of Gaddafi forces around and inside cities, to give Libyan people the freedom to choose,” said Mustafa Abdel Jalil, chairman of the rebels’ Transitional National Council in Benghazi.

“Our main aim is to remove the siege from the cities,” he said.

 Abdel Jalil, who formerly served as Gaddafi’s justice minister before defecting last month amid a popular uprising, stressed that the rebels remain steadfast in their demand that Gaddafi and his family leave power. And he said the rebels would need weapons deliveries if the more heavily armed and better organized government forces keep fighting.

In a joint news conference with U.N. special envoy Abdul-Illah Khatib, a former Jordanian foreign minister, Abdel Jalil said: “We have no objection to a cease-fire but on condition that Libyans in western cities have full freedom in expressing their views.” He said that if the inhabitants of the besieged cities are allowed to express themselves, “the world will see that they will choose freedom.”

The rebels’ ultimate goal remains the departure of Gaddafi, Abdel Jalil said. He told reporters: “Our aim is to liberate all of Libya and have a sovereign Libya with the capital in Tripoli.”

He made the comments as Khatib visited the rebel stronghold of Benghazi for talks on a cease-fire and a political solution to the six-week-old Libyan crisis. Khatib said he met Thursday with members of Gaddafi’s government in Tripoli before conferring with the Transitional National Council here Friday. He said he would convey the results of the meetings to U.N. Secretary General Ban Ki-moon. It was his second visit with opposition leaders, he said.

Khatib said he told government officials in Tripoli that a cease-fire would need to be “credible,” “effective” and “very final.”

“Each party, of course, says that they will respect the terms of the cease-fire if the other one does, and that is the real challenge,” he said.

With the rebels again on the defensive after having recaptured Ajdabiya over the weekend, opposition officials took some solace in the defection Wednesday of Kusa, 62, who headed Gaddafi’s intelligence apparatus for 15 years before becoming foreign minister in 2009. They joined U.S. and British officials in hailing the move as evidence that the Gaddafi regime was crumbling from within, and rumors swirled around the Libyan capital Thursday that as many as 15 top regime officials had fled to Tunisia and were seeking refuge in the West.

But it was unclear whether Kusa’s departure would have an immediate effect on the balance of power on the ground or trigger the mass defections that U.S. officials said they were hoping for.

While mysterious bursts of gunfire are relatively common during the night in Tripoli, the shooting early Friday appeared to be more intense than usual. There were conflicting reports about what sparked the firing. Some suggested that protesters had attempted to take to the streets again for the first time since the uprising in the capital was brutally crushed nearly a month ago. Others spoke of an attack on Gaddafi’s compound.

Witnesses told Reuters they had seen “pools of blood” outside the compound that were washed away by morning. One said sharpshooters had been positioned on high buildings around the capital, perhaps to preempt any possible demonstrations after Friday prayers, which served as a rallying point for opposition protests before they were stamped out. Journalists who attempted to leave their hotel unaccompanied by government minders were turned back by armed men.

There were also no new reports of defections. One of those who had been named as a possible defector, intelligence chief Abuzayd Omar Durdah, called state television late Thursday to proclaim his loyalty to the regime. “I am in Libya, and I am going to stay in it,” he said.

Kusa was the most senior Gaddafi minister to abandon the regime, and his defection in London prompted appeals by U.S. and British officials for other top figures to follow him into exile.

On Friday, a British government official told The Washington Post that Mohammed Ismail, a senior aide and discreet fixer for Gaddafi’s powerful son, Saif al-Islam Gaddafi, was in London recently to talk to government officials.

British media reports speculated that Ismail made the trip to open lines of communication with the West, perhaps to explore exit strategies for one or more members of the Gaddafi family.

A spokeswoman at the British Foreign Office declined to comment on the visit, saying: “We’re not going to provide running commentary on our contacts with Libyan officials.”

According to the Associated Press, British officials contacted Ismail after learning that he was in Britain to visit relatives and told him Gaddafi must quit. Two officials insisted that Ismail had not been sent to London on a mission for Gaddafi and said the aide returned to Libya earlier this week, AP reported.

The Gaddafi government announced a cease-fire with the rebels a day after the U.N. Security Council on March 17 authorized a no-fly zone over Libya and “all necessary measures” to protect civilians. But Gaddafi’s troops continued to attack rebel-held cities.

Abdel Jalil, the rebel council leader, spoke Friday as if he expected the current fighting to continue. Despite the pounding rebels took this week, he said, “We have full confidence in our forces and our determination that we will be able to unseat Gaddafi and his regime.”

Abdel Jalil also expressed concern over the fate of prisoners taken by Gaddafi forces during the fighting. While the International Committee of the Red Cross has been allowed to visit rebel-held prisoners in Benghazi, he said, no such access has been given by the other side.

Opposition leaders estimate that thousands of prisoners are being held by the Gaddafi regime.

Seeking cash to buy desperately needed supplies, the rebel government is prepared to produce 100,000 barrels of oil a day for export, which would be marketed by Qatar, a Libyan opposition official said Friday.

“The Qatar government agreed, and it is signed, that they’d market the crude oil for us,” said Ali Tarhouni, the opposition official responsible for finance, economics and oil. “The only delay is finding the vessels that will carry the oil.”

However, he said, the opposition’s ability to profit from such exports is limited by sanctions imposed on Libyan oil, from which rebel-held areas are not exempt. Tarhouni said the rebel government is asking the United Nations to lift the sanctions.

Until then, he said, proceeds from sales would go into an escrow account, through which the rebels could receive food, medical supplies, fuel and other humanitarian provisions.

The rebels this week recaptured two oil ports, Ras Lanuf and Brega, then quickly lost control of them in a counteroffensive by Gaddafi loyalists.

But Tarhouni said oil fields in the southeastern part of the country are firmly in rebel hands and can produce crude for shipment via Tobruk, a city near the Egyptian border.

Qatar, a small Persian Gulf emirate, has joined the Western-led coalition enforcing the U.N. no-fly zone and is the only Arab country so far to recognize the rebel government.

 Tarhouni said the interim government has also requested recognition by the United Nations as Libya’s legitimate representative.

Sly reported from Benghazi. Branigin reported from Washington. Correspondent Karla Adam contributed from London.