Libyan army convoy crosses into Niger

They are believed to include Kadhafi's internal security chief Mansour Daw, who was earlier reported to be in the loyalist stronghold Bani Walid, with at least two of the fallen strongman's sons.

Meanwhile, anti-Kadhafi fighters were preparing on Tuesday to strike at Bani Walid, southeast of Tripoli. Abdullah Kenshil, the chief negotiator for Libya's new government, said civilians were being held hostage in the centre of the town, in administrative buildings and in five or six nearby villages.

"Kadhafi's soldiers have also closed the gates of the town and are not letting families leave," he said. "That worries us, we don't want to kill civilians in the attack."

Negotiations for the surrender of Bani Walid, southeast of Tripoli, broke down late Sunday but there was little movement on that front on Monday despite concerns that local families could be held as human shields.

Local officials said most senior figures had fled Bani Walid with Kadhafi's most prominent son, Seif al-Islam, who is said to have left a few days before for Sabha, further south, that is still in the hands of regime loyalists.