Clashes have broken out near Muammar Gaddafi's compound in Tripoli, a day after rebels poured into the Libyan capital in a stunning advance that met little resistance from the regime's defenders.
Rebel spokesman Mohammed Abdel-Rahman said government tanks emerged from the complex, known as Bab al-Aziziya, and opened fire.
An Associated Press reporter at the nearby Rixos Hotel where foreign journalists stay could hear gunfire and loud explosions from the direction of the complex.
Meanwhile, opposition fighters captured Gaddafi's son and one-time heir apparent, Saif al-Islam. The prosecutor at the International Criminal Court in the Netherlands said he would contact the rebels to discuss Saif's handover for trial on charges of crimes against humanity.
Tripoli resident Moammar al-Warfali, whose family home is next to Bab al-Aziziya, said tanks rolled out from the compound in the early morning after a group of rebels tried to get in. He said there appeared to be only a few tanks belonging to the remaining Gaddafi forces that have not fled or surrendered.
The rebels seized control of most of Tripoli in a lightning advance on Sunday, and euphoric residents celebrate in the capital's Green Square, the symbolic hear of the Gaddafi regime.
Gaddafi's defenders quickly melted away as his 42-year rule crumbled, but the leader's whereabouts were unknown and pockets of resistance remained.
Mr Abdel-Rahman, who is in Tripoli with rebel forces, cautioned that Gaddafi troops still pose a threat to rebels, and that as long as Gaddafi remains on the run the "danger is still there."
By the early hours of Monday, opposition fighters controlled most of the capital.
President Barack Obama said Libya is "slipping from the grasp of a tyrant" and urged Gaddafi to relinquish power to prevent more bloodshed.