Forces of Libyan strongman Muammar Gaddafi began attacking on Wednesday the rebel-held town of Zintan, 120 kilometres (75 miles) southwest of Tripoli, an independent witness told AFP by telephone.
"Things are starting at Zintan. There is some tank fire a few kilometres south of the town and the sound of Grad-type rockets being launched in salvos, as well as an exchange of small-arms fire," he said.
"Local people say some 40 army vehicles are on the south side of town with tanks and rocket-launchers, while in the north a column of some 15 tanks approached during the night."
The witness, who said he could observe the scene from some 10 kilometres west of Zintan, was pessimistic about the rebels' chances of repelling the attack.
"From what I can see they are badly organised and badly armed, just villagers on guard," he said. "Where I am there are around 15 guys with five Kalashnikovs, an Italian rifle and three old shotguns."
"The rebels dispatched a number of vehicles towards the shooting in the south," the witness added. "I saw a truck with anti-aircraft guns rush off, but another vehicle failed to start.
Zintan was the first city in western Libya to join the anti-regime protests a day after the revolt against Gaddafi‘s autocratic 41-year rule erupted on 15 February in the eastern coastal city of Benghazi.