Rebel forces have fought their way towards Muammar Gaddafi's hometown of Sirte, a key government stronghold guarding the road to the capital Tripoli.
Their rapid advance came on the back of international air strikes that have battered Gaddafi's air force, armour and troops over the past week. The rebels have now recaptured all the territory they lost over the past week and brought them closer than ever to Sirte - within 60 miles.
Some residents were fleeing the city of 100,000, as soldiers from a brigade commanded by Gaddafi's son al-Saadi streamed to positions on the city's outskirts to defend it, witnesses said. Sirte - where a significant air and military base is located - was hit by air strikes on Sunday night and Monday morning, witnesses said.
Nato's commander for the operation, Lieutenant General Charles Bouchard of Canada, deflected suggestions that international air strikes against Gaddafi's forces were essentially providing air cover for advancing rebels, insisting that the military alliance's mission was purely designed to protect civilians.
"Our goal is to protect and help the civilians and population centres under the threat of attack," he said.
Over the years, Gaddafi has made Sirte effectively Libya's second capital and its fall to the rebels would largely open their way to move on the capital, Tripoli, 250 miles to the north-west. The rebels have recovered hundreds of miles of flat, uninhabited territory at record speeds after Gaddafi's forces were forced to pull back by the international strikes that began March 19.
International air forces flew 110 missions late on Sunday and early on Monday - 75 of them strike missions. Targets included Gaddafi ammunition stores, air defences and ground forces, including vehicles and tanks, an official said.
International air strikes also hit Sebha, 400 miles south of Tripoli. The area remains strongly loyal to Gaddafi and is a major transit point for ethnic Tuareg fighters from Mali and Niger fighting for the government.
Libya accused Nato of becoming directly involved in the fighting.
"This is the objective of the coalition now, it is not to protect civilians because now they are directly fighting against the armed forces," Khaled Kaim, the deputy foreign minister, said in the capital, Tripoli. "They are trying to push the country to the brink of a civil war."
