Reports from Libya say NATO has launched airstrikes around the desert town of Bani Walid, one of the last strongholds of the former dictator Muammar Gaddafi.
A Reuters correspondent on the outskirts of the town says he witnessed five missiles.
Bani Walid, 150km southeast of the capital, has been under siege for days.
Scores of loyalists have been putting up resistance.
A deadline of Saturday set by the National Transitional Council for Gaddafi strongholds to surrender, has expired.
NTC fighters said they would assault the town it did not yield.
NATO confirmed its aircraft were flying missions over Bani Walid, but would not comment on any airstrikes.
NTC chief now in capital
Meanwhile, NTC head Mustafa Abdul-Jalil has flown to the capital, Tripoli, for the first time since rebels took control of the city on 23 August.
He was greeted by hundreds of supporters.
Mr Abdul-Jalil has until now remained in Benghazi and his presence in the capital is aimed at sending a message about his authority.
Deputy Mayor Usama El-Abed described Mr Abdul-Jalil's arrival as a historic moment.