Haftar's forces launched an offensive in April to try to wrest Tripoli from forces backing the Government of National Accord (GNA).

Pro-GNA armed groups have weathered the initial onslaught and fighting has since remained deadlocked on the southern outskirts of the city, with both sides resorting to air strikes.

Pro-GNA forces on Thursday night "launched a special operation in the Al-Yarmuk and Salaheddine" areas of Tripoli's southern suburbs during which they "retook control of key Haftar positions", GNA spokesman Mustafa al-Mejii told AFP.

"We destroyed three armoured vehicles and seized four tanks," he said, adding that nine pro-GNA fighters were killed, five of them in an air strike.

According to Mejii, several of Haftar forces were killed or wounded during the operation while six were captured.

Haftar's self-styled Libyan National Army does not release its casualty tolls.

The World Health Organization says that fighting since April has left nearly 1,100 people dead and wounded more than 5,750, and forced more than 100,000 civilians to flee their homes.