The GNA has with Turkish help made sudden strides in recent weeks, seizing a string of towns from warlord Khalifa Haftar's militias, capturing the strategically important Watiya airbase and destroying several of its Russian-made air defence systems.
Libya's internationally recognised government retook parts of southern Tripoli on Friday from the militias loyal to warlord Khalifa Haftar, whose 13-month campaign to seize the capital is under ever-greater pressure.
Fighters for the Government of National Accord (GNA) said they had advanced into several districts and overrun a military camp.
The GNA has with Turkish help made sudden strides in recent weeks, seizing a string of towns from Haftar militias, capturing the strategically important Watiya airbase and destroying several of its Russian-made air defence systems.
Haftar, backed by the United Arab Emirates, Russia and Egypt, has promised to respond with a massive air campaign and on Thursday its spokesman Ahmed Mismari said four warplanes had become newly available.
Ankara has warned the warlord and his militias, saying any attack on Turkish interests in the country will have "grave consequences."
As diplomats warned of the risk of a new round of escalation with the warring sides' external backers pouring in new weaponry, the focus of the conflict shifted towards Tarhouna, the biggest remaining Haftar stronghold in northwest Libya.
The GNA took Asaba, which lies on a major supply route to Tarhouna on Thursday, putting more pressure on Haftar's militias in the town, which has been subjected to bombardment for weeks.
The United Nations Libya mission said it was following the mobilisation around Tarhouna with "great concern," warning all parties against any acts of retribution in a statement the United States said it supported.