TRIPOLI, Libya - Rival militias clashed on the outskirts of the Libyan capital for a fourth day Sunday in the most sustained violence since the capture and killing of Moammar Gadhafi last month.

The fighting, which has killed at least six people since late last week, raised new concerns about the ability of Libya's transitional government to disarm thousands of fighters and restore order after an eight-month civil war.

Libya's interim leader, Mustafa Abdul-Jalil, said his National Transitional Council brought together elders from the feuding areas -- the coastal city of Zawiya and the nearby tribal lands of Warshefana -- over the weekend and that the dispute has been resolved. "I want to assure the Libyan people that everything is under control," he said Sunday.

However, as he spoke, fighting continued.

Heavy gunfire and explosions of rocket-propelled grenades were heard over hours Sunday in the area between the Warshefana lands, about 30 kilometres west of Tripoli, and Zawiya, another 15 kilometres to the west. White smoke rose into the air.

At one point, the two sides were battling for control of a major military camp of the ousted regime, said a fighter from Tripoli. The camp, once a base of elite forces commanded by one of Gadhafi's sons, Khamis, is located on a highway midway between Tripoli and Zawiya.

Two men from Warshefana were killed by friendly fire Sunday, another fighter said. This brought the overall death toll to at least six since the dispute between the communities erupted.

The reason for the initial clash remains unclear, though accusations have been flying, including that some of the Warshefana had links to the old regime. At one point last week, fighters from Zawiya entered Warshefana and seized weapons. In retaliation, Warshefana fighters set up random checkpoints and fired at the main highway.

On Sunday evening, dozens of Warshefana fighters assembled and said they would march on Zawiya. "We'll be in Zawiya tonight," they chanted before moving toward the city, armed with assault rifles and rocket-propelled grenades.

Zawiya fighters, meanwhile, manned roadblocks on the outskirts of their city at intervals of about 200 metres. Groups of jumpy armed men, some brandishing RPGs, crowded around the checkpoints. Fighters searched trunks of cars and checked IDs.

Abdul-Jalil said the NTC has established a committee to address the grievances of both sides. He said the fighting was sparked by young men behaving irresponsibly, but he did not elaborate.

Since the Oct. 20 death of Gadhafi, there have been a number of violent clashes between fighters, including a deadly shootout at a Tripoli hospital. Residents of the capital have also become increasingly annoyed with fighters from other areas of Libya who have taken over prime locations in the city, including a gated seaside resort village.

Despite the growing tensions, Abdul-Jalil and other NTC leaders have said they cannot disarm the fighters quickly.

Noting high unemployment among the armed men, Abdul-Jalil said the new government must offer alternatives first, including jobs, study and training.