The convoy of Saif al-Islam Gaddafy, a key son of Libya's toppled dictator Muammar Gaddafi, has been encircled and attacked by rebel forces, reports say.

Shortly after Sirte was overwhelmed by the rebel forces, and Muammar Gaddafi was captured and died of his wounds earlier on Thursday, Seif al-Islam was believed to still be at large in the southern Libya desert, a Transitional National Council member has told al-Jazeera.

Reports cited by the BBC Thursday night, however, say that Seif al-Islam Gaddafi, said to be fleeing Sirte in a convoy, has been encircled and is under attack.

Seif al-Islam was last known to have been in the area of Bani Walid and was believed to be "in the desert" around the town, Abdelmajid Saif al-Nasr, a TNC official, has told the Qatar-based TV channel.

Seif al-Islam is wanted by the International Criminal Court for crimes against humanity, He had been his father's likely choice to succeed him as Libya's leader.

Meanwhile, TNC official Abdel Majid Mlegta has told Reuters that Col Gaddafi's son Mutassim, who died during his father's capture, was killed by NTC forces. "He was trying to fight back and he was resisting them," he said, as cited by Al Jazeera.