Rebels overran Muammar Gaddafi’s fortified Bab al-Azizya headquarters in Tripoli after heavy fighting Tuesday and immediately hoisted their flag to mark the symbolic end to the strongman's 42-year rule.

As rebel leaders proclaimed they had "won the battle" in Tripoli, fighters celebrated by firing automatic weapons into the air, chanting "Allahu akbar" (God is greatest), and raiding the armoury for ammunition, pistols and rifles.

The defenders had fled, and there was no immediate word on the whereabouts of Gaddafi or his family after the insurgents late afternoon breached the defences as part of a massive assault that began in the morning.

"We have won the battle," Abdel Hakim Belhaj, the insurgents' Tripoli commander told Al-Jazeera television from inside the complex.

"The military battle is over now," he said.

In the rebels' eastern bastion of Benghazi, where residents poured onto the streets in celebration, commander Colonel Ahmed Omar Bani said there had been no trace of Gaddafi or his family.

"Bab al-Azizya is fully under our control now. Colonel Gaddafi and his sons were not there; there is nobody," Bani said. "No one knows where they are."

An AFP correspondent said rebels first breached the surrounding cement walls before entering inside.

"They have taken Bab al-Azizya. Completely. It is finished. It is an incredible sight," he said, adding that the bodies of a number of apparent Gaddafi fighters were lying inside, as were wounded people.

Footage from satellite channels showed a young rebel climbing atop a huge sculpture of a fist gripping an airplane -- a symbol of a US attack on the compound in 1986 -- trying to break off a piece.

Another rebel proudly brandished a seized rifle with a gold-plated barrel and stock saying "Gaddafi people killed us with it."

As young men tore up a poster portrait of Gaddafi, others were seen kicking around metallic mask of Gaddafi. One young man, a green bandana around his head, then picked it up and held it above his head like a trophy, flashing a smile.

Amid reports that ordinary citizens were beginning to stream into the complex of several hectares (acres), rebel television Al-Ahrar called on people to stay away so that insurgent fighters could mop up inside.

It also urged police in Tripoli to remain at their posts in order to guarantee security.

A rebel official in the western city of Misrata said that "at the same house used by Gaddafi before to describe the Libyan people as rats, today the independence flag is flying on its roof."

He was referring to a speech by Gaddafi soon after the rebellion was launched in mid-February in which he referred to those rising up against him as "rats."

The fighting for Gaddafi's headquarters was the most intense in the city since rebel fighters in their hundreds came surging through its gates three days ago.

The sky in the afternoon was filled with the sound of heavy and light machine guns as well as mortars, with the overhead roar of NATO jets, though it was unclear if they carried out air strikes.

Even two kilometres (about a mile) from the fighting, the almost constant whistle of falling bullets could be hear from the rooftops, as the city's mosques chanted "Allahu Akbar" (God is the greatest).

Rebel leaders said fighters from their western bastion of Misrata, renowned for their prowess after breaking a months-long siege of the port city by Gaddafi's forces, had joined Tripoli rebels in the assault, which also saw the deployment of tanks captured from loyalist forces.

On the eastern front, Libyan rebels on Tuesday overran the eastern oil hub of Ras Lanuf on the road to Moamer Gaddafi's hometown of Sirte, their military spokesman Colonel Ahmed Omar Bani said.

"We are now in Ras Lanuf," Bani said, adding he hoped insurgents would soon reach Bin Jawad, a hamlet just east of Sirte and almost halfway between the rebel-held cities of Benghazi and Misrata.

Bab al-Azizya had been the site chosen very early Tuesday by Gaddafi's son, Seif al-Islam, to make an appearance before journalists to refute reports that he had been arrested by the rebels.

"Tripoli is under our control. Everyone should rest assured. All is well in Tripoli," Seif said at the compound, smiling broadly and flashing the V-for-victory sign.

"I am here to refute the lies," the 39-year-old said about reports of his arrest, and accused the West of waging a "technological and media war to cause chaos and terror in Libya."

Seif, like his father, is wanted by the International Criminal Court (ICC) for crimes against humanity. He said Gaddafi and his entire family were still in Tripoli, denying rumours he had fled but without specifying the exact location.

His comments were backed up by the Russian head of world chess who said on Tuesday Gaddafi had told him in a telephone call that he was in Tripoli and did not intend to leave the country.

"I am alive and healthy. I am in Tripoli and do not intend to leave Libya. Do not believe the lying reports by Western television companies," Kirsan Ilyumzhinov quoted Gaddafi as saying in the conversation, the Interfax news agency reported. Ilyumzhinov had met Gaddafi in Tripoli in June.

In Paris, French President Nicolas Sarkozy said he had agreed with his US counterpart Barack Obama to continue military action against Gaddafi until he lays down his weapons.

Sarkozy's Elysee Palace said in a statement that the two leaders had held telephonic talks during which they "agreed to pursue their military effort in support of the legitimate Libyan authorities for as long as Gaddafi and his clan have not put down their arms."

They were referring to the NATO-led bombing campaign launched in March under a UN mandate to protect civilians in Libya.