Violent clashes raged Tuesday south of the Libyan capital Tripoli, marking an uptick in fighting between forces loyal to commander Khalifa Haftar and those battling on the government's side.
Heavy artillery fire could be heard from the city centre as the most intense fighting took place since May 6, when the holy Muslim month of Ramadan started.
More than six weeks since Haftar's forces launched an assault on the capital, fighters backing the UN-recognised Government of National Accord made advances in the southern Salaheddin neighbourhood.
AFP journalists on the front lines estimated pro-GNA forces progressed by two or three kilometres (up to two miles) in the residential district.
Moustafa al-Mejii, a GNA spokesman, said fighter planes supported ground forces in their advance, carrying out strikes against tanks and heavy weapons in a barracks.
Weeks of fighting have killed 510 people and wounded 2,467, according to the latest toll from the World Health Organization.
More than 75,000 people have fled their homes, according to the United Nations, while 100,000 are trapped by the conflict.
On Tuesday the UN's envoy for Libya, Ghassan Salame, warned "the violence on the outskirts of Tripoli is just the start of a long and bloody war."
Without immediate action to stop the flow of arms, he said, "Libya will descend into civil war which could potentially lead to a Hobbesian all-against-all state of chaos or partition of the country."