After a euphoric night for the rebels, heavy fighting broke out yesterday near Gaddafi's compound, Bab al-Aziziya, as forces still loyal to the dictator fought back.

Rebels spokesman Muhammad Abdel-Rahman said tanks began firing from the compound early in the morning. One of Gaddafi's sons, Khamis, was reported to be leading loyalist troops in the counter-attack.

Later, however, a local resident told AP there appeared to be only a few tanks belonging to Gaddafi forces that had not fled or surrendered.

''When I climb the stairs and look at it from the roof, I see nothing at Bab al-Aziziya,'' said Moammar al-Warfali. ''NATO has demolished it all and nothing remains.''

The head of the rebels' ruling council, Mustafa Abdel Jalil, told a news conference in Benghazi: ''The era of Gaddafi is over.'' He called on rebel fighters to avoid reprisals, respect human rights and treat prisoners of war well.

NATO, meanwhile, said it would continue air strikes in support of the rebels and would monitor remaining threats posed by Gaddafi forces.

Earlier, in Tripoli's central Green Square - the site of many manufactured rallies in support of Gaddafi - jubilant Libyans tore down posters of him and stomped on them.

Rebel leaders said the presidential guard protecting the Libyan leader had surrendered and that their forces controlled many parts of the city.

The International Criminal Court confirmed one of Gaddafi's sons, Saif al-Islam, had been detained. Rebels said another son had surrendered.

The longest-serving leader in both Africa and the Arab world, Gaddafi has ruled Libya since he toppled King Idris I in a bloodless coup at age 27.

His downfall, when it comes, will make him the latest Arab dictator to be swept aside by the tide of public protest, following the fall of Tunisia's Zine al-Abidine Ben Ali and Egypt's Hosni Mubarak in February.

After six months of inconclusive fighting, the assault on the capital unfolded at a breakneck pace, with insurgents capturing a base of the vaunted Khamis Brigade where they had expected to meet resistance, then speeding towards Tripoli and then through several neighbourhoods virtually unopposed.

Gaddafi's whereabouts were not clear last night. A diplomatic source who met him within the past two weeks said he could still be in the compound. Others said he had fled to his coastal home town of Sirte.

Gaddafi issued a series of defiant audio statements on Sunday night, calling on people to ''save Tripoli'' from a rebel offensive.

Mahmoud Hamza, a senior Foreign Ministry official, acknowledged that ''it is getting near the end now''. But he said that the Gaddafi forces had not given up.

United States President Barack Obama said Gaddafi and his inner circle had ''to recognise that their rule has come to an end''.

He also called on the rebels to avoid civilian casualties as they took control of the country.

''Tonight, the momentum against the Gaddafi regime has reached a tipping point,'' Mr Obama said. ''Tripoli is slipping from the grasp of a tyrant.''

British Prime Minister David Cameron said: ''Gaddafi must stop fighting, without conditions, and clearly show that he has given up any claim to control Libya. His regime is falling apart and in full retreat.''

In Canberra, Prime Minister Julia Gillard told Parliament that Australia stood ready to help Libya recover from the civil war and ''develop a tolerant, inclusive, democratic society''.

With NEW YORK TIMES, GUARDIAN, AGENCIES