Mr Abdul Jalil was greeted by hundreds of cheering, flag-waving supporters.

Until now he had remained in the eastern city of Benghazi. His presence in the capital is aimed at sending a message about his authority.

To the south, Nato aircraft bombed Bani Walid, one of the last pro-Gaddafi strongholds, following fighting there. Separately, the IMF has recognised Mr Abdul Jalil's National Transitional Council (NTC) as the new government of Libya.

There were chaotic scenes as Mr Abdul Jalil emerged from the aircraft that had brought him from Benghazi. Crowds of people surged forward trying to get close to him as soldiers struggled to maintain order.

He now faces big challenges as he tries to stabilise the country and form an effective national administration. Anti-Gaddafi forces now control most of the country - the colonel's whereabouts are unknown. But his fighters have been putting up fierce resistance in Bani Walid, one of four towns they still control.

The attackers say they are facing heavy artillery and rockets from Gaddafi loyalists inside the town. But they insist they are making progress and their military spokesman Abdulrahman Busin says the town will fall imminently.