Libya's interior minister and nine members of his family have flown into Cairo on their private plane in what appeared to be the highest-level defection from Muammar Gaddafi's regime in months.

Egyptian airport officials said Nassr al-Mabrouk Abdullah had entered on a tourist visa.

No Libyan embassy officials greeted him at the airport. One embassy official said they were not aware of his plans to visit Egypt. All officials spoke on condition of anonymity because they were not authorised to speak to the media.

The minister flew in from Tunisia, which borders Libya.

The apparent defection came days after Libya's rebels made their most dramatic advances in months in western towns and cities close to the capital, Tripoli.

On Saturday, rebels from the western mountains near Tunisia pushed into the strategic city of Zawiya, 30 miles from Tripoli, for the first time since the uprising against Gaddafi began in February.

On Sunday, the rebels claimed to have captured at least two other towns near Tripoli that straddle key overland supply routes for the capital. The roads are seen as critical for supplying the regime because of Nato's no-fly zone.

Rebels have claimed they are trying to cut off all Gaddafi's supply routes.

Rebel officials said on Sunday that they had captured the town of Gharyan, 50 miles south of Tripoli, which sits on the supply road from southern Libya.

Omar Obeid, field commander for the Sabratha area 20 miles west of Zawiya on the coast, said rebels had taken up positions in houses along a major supply route that connected the Ras Ajdir border crossing with Tunisia to Tripoli. The same road runs through Zawiya, where rebels could also block it if they manage to take full control of the city.

Rebels said they had also captured the town of Surman, near Sabratha, to the south-east.