A rebel spokesman in the Nafusa mountains said there had been heavy fighting on the outskirts of the strategic town of Bir al-Ghanam.

Meanwhile the International Criminal Court is to decide whether to issue an arrest warrant for Col Gaddafi.

A decision by a three-judge panel is expected at 1100 GMT. The ICC's chief prosecutor has also requested arrest warrants for Col Gaddafi's son, Saif al-Islam, and the head of Libyan intelligence, Abdullah Senussi.

The warrants are for alleged crimes against humanity committed against opponents of the regime.

The international military operation in Libya entered its 100th day on Monday, with the rebels still struggling to take advantage of coalition air strikes on Col Gaddafi's infrastructure.