* Western mountain fighters push towards Gaddafi-held town
* NATO aircraft heard overhead
* Gaddafi's forces responding with rocket fire
By Peter Graff
AL-QALAA, Libya, July 6 (Reuters) - Hundreds of Libyan rebels launched a massed offensive in the mountains southwest of Tripoli on Wednesday to seize a village held by Muammar Gaddafi's forces and push the front line closer to the capital.
Rebels arrived at the front at first light in scores of Toyota pick-up trucks, many with large-calibre anti-aircraft guns or home-made rocket launchers welded onto the truck beds. Several tanks also came on the backs of lorries.
The rebels began firing rockets and mortars at dawn, cries of "Allahu Akbar!" or "God is greatest!" echoing through groves of olive, almond and fig trees with each outgoing blast.
Gaddafi's forces responded with intermittent volleys of Grad tactical surface-to-surface rockets. Clouds of black smoke came from the hillsides where the incoming rounds exploded.
Five months into their revolt, rebels have gained little ground elsewhere but have made steady progress here on a high plateau which juts several hundred kilometres (miles) into Libya from the Tunisian border and overlooks a coastal plain leading to Tripoli.
The rebels' aim on Wednesday was to push 10 km (6 miles) from the town of Al-Qalaa to the village of Al-Qawalish, which is held by Gaddafi's forces.
The fighters were pushing south-east, away from the capital, but taking Al-Qawalish is strategically important because beyond it, further to the east, is the larger town of Garyan which controls the main highway north to the capital.
Throughout the morning, rebels advanced on foot through hilly wasteland and orchards towards Al-Qawalish carrying old rifles and makeshift rocket launchers.
The hills reverberated with call-and-response chants of "There is no God but God!"
After several hours, the rebels had advanced a couple of kilometres towards Al-Qawalish, and there was no sign of any casualties.
NATO warplanes could be heard in the sky, but it could not be confirmed if the aircraft were coordinating with the rebels.
(Editing by Sonya Hepinstall)