A son of Muammar Gaddafi who rebels said they had captured appeared with cheering supporters in Tripoli, giving a boost to forces loyal to the veteran leader trying to fight off insurgents who say they control most of the capital. 

Saif al-Islam, who has been seen as his father's heir apparent, visited the Tripoli hotel where foreign journalists are staying to declare that the government was winning the battle against the rebels.

He took journalists to his father's Bab al-Aziziyah stronghold. Television footage showed Saif pumping his fists in the air, smiling, waving and shaking hands with supporters, as well as holding his arms aloft with each hand making the V for victory sign.

'We broke the back of the rebels. It was a trap. We gave them a hard time, so we are winning,' Saif said.     

Saif's arrest had been reported both by rebels and the International Criminal Court in The Hague and his appearance before the foreign media raised questions as to the rebels' credibility.      

He said that Tripoli was under government control and that he did not care about the arrest warrant issued by the International Criminal Court seeking him and his father for crimes against humanity.

Gaddafi himself has not been seen in public since some time before the rebels arrived in the capital at the weekend. But when asked if his father was safe and well in Tripoli, Saif told journalists: 'Of course.'           

World leaders urged Gaddafi, 69, to surrender to prevent more bloodshed and appealed for an orderly transition of power, as the six-month-old battle for control of the oil-producing North African nation appeared to enter its final stages.

Rebels swept into Tripoli two days ago in tandem with an uprising within the city. Reuters reporters saw firefights and clashes with heavy weapons, including anti-aircraft guns, as rebels tried to flush out snipers and pockets of resistance.

Hundreds seem to have been killed or wounded since Saturday. But Gaddafi tanks and sharpshooters appeared to hold only small areas, mainly around the heavily fortified Bab al-Aziziyah compound in central Tripoli.

Civilians, who had mobbed the streets on Sunday to cheer the end of dictatorship, stayed indoors as machinegun fire and explosions punctuated some of the heaviest fighting of the Arab Spring uprisings that have been reshaping the Middle East.

US President Barack Obama, saying the conflict was not over yet, cautioned rebels against exacting revenge for Gaddafi's brutal rule. 'True justice will not come from reprisals and violence,' he said.

The president also made plain that the United States would oppose any group within the loose coalition of rebels from imposing its power over other parts of Libyan society.

'Above all we will call for an inclusive transition that leads to a democratic Libya,' Obama said. 

In an audio broadcast on Sunday before state TV went off the air, Gaddafi said he would stay in Tripoli 'until the end'.

There has been speculation, however, he might seek refuge in his home region around Sirte, or abroad.      

In a sign Gaddafi allies were still determined to fight, Nato said government forces fired three Scud-type missiles from the area of Sirte towards the rebel-held city of Misrata.

Bab al-Aziziyah, a huge complex where some believe Gaddafi might be hiding, was the focal point of fighting in Tripoli.

'I don't imagine the Bab al-Aziziyah compound will fall easily and I imagine there will be a fierce fight,' Abdel Hafiz Ghoga, spokesman for the rebel National Transitional Council, said in an interview aired by Al-Jazeera.     

The Arab network, quoting its correspondent, said violent clashes were also reported near the oil town of Brega.

Rebels had initially said they held three of Gaddafi's sons, including Saif al-Islam. Al-Jazeera TV said that one of them, Mohammed, had escaped, adding that the body of another son, military commander Khamis, might have been found along with that of powerful intelligence chief Abdullah al-Senussi. - Reuters