Libyan helicopter gunships fired on a rebel force advancing west toward the capital along the Mediterranean coastline and forces loyal to leader Muammar Gaddafi fought intense ground battles with the rival fighters.
The opposition force pushed out of the rebel-held eastern half of Libya late last week for the first time and has been cutting a path west toward Tripoli. On the way, they secured control of two important oil ports at Brega and Ras Lanouf and by Sunday, the rebels were advancing farther west when they were hit by the helicopter fire and confrontations with ground forces.
The uprising against Gaddafi, which began just days after President Hosni Mubarak was ousted by protesters in neighbouring Egypt, has been sliding rapidly toward civil war, making it the bloodiest episode in the Middle East's wave of unrest.
The seesawing battles for towns and oil installations along the coastline signalled that Libya's fighting could be prolonged, compared with the ousting of Mubarak after just 18 days. The protesters-turned-rebels - backed by mutinous army units and armed with weaponry seized from storehouses - are going on the offensive to try to topple Gaddafi's 41-year-old regime.
At the same time, pro-Gaddafi forces have conducted counter-offensives to try to retake the oil port of Brega and the rebel-held city of Zawiya west of Tripoli - where bloody street battles were reported over the weekend.
On Sunday, government airstrikes hit the town of Ras Lanouf and ground troops loyal to Gaddafi retook the town of Bin Jawwad, about 110 miles east of Gaddafi's hometown and stronghold of Sirte, which could prove to be a decisive battleground.
From the edge of Bin Jawwad, a steady barrage of rockets and artillery fired by pro-Gaddafi forces thumped to the ground. About 50 rebel fighters were trapped inside a mosque, and their comrades who had retreated to the edge of the city sent 20 pick-up trucks back through the bombardment to try to rescue them. One of the trucks was hit.
A warplane attacked a small military base at Ras Lanouf and destroyed three hangars and a small building. Regime forces shelled rebel positions there with rockets and artillery. Ambulances sped toward the town and rebels moved trucks and four multiple-rocket launchers toward the front lines.
Four people were killed in the fighting in those two towns, and a French journalist for France 24 TV was wounded, hospital officials said.
In Tripoli, the city of two million that is most firmly in Gaddafi's grip, residents awoke before dawn to the crackle of unusually heavy and sustained gunfire that lasted for at least two hours. Some of the gunfire was heard around the sprawling Bab al-Aziziya military camp where Gaddafi lives, giving rise to speculation that there may have been some sort of internal fighting within the forces defending the Libyan leader inside his fortress-like barracks. Gaddafi's whereabouts were unknown.