Opposition forces in Benghazi say 30 people were killed and many more wounded when troops loyal to longtime leader Muammar Gaddafi attacked the western outskirts of the rebel stronghold in the hours after the UN Security Council approved military action against him.

Residents of the city expressed anger with the international community, saying it had acted too slowly to prevent one final assault from Gaddafi.

But opposition fighters more than held their own, driving back the loyalist troops - some of whom may have remained in Benghazi all along as "sleeper cells" - and capturing at least two tanks.