Tripol - Air force units of Libya's unity government launched an operation on Saturday to cut off potential escape routes for jihadists holed up in the coastal city of Sirte, loyalist forces said.
The forces of the Government of National Accord (GNA), on their Facebook page, said the surveillance operation covered central Libya as well as the western region up to the border with Tunisia.
Pro-GNA forces, backed since early August by US air strikes, began an assault in mid-May to expel the Islamic State group from its Sirte stronghold.
They fought their way into Sirte on June 9 and have since faced a barrage of sniper fire, suicide bombings and booby traps, but have pinned down the jihadists in a downtown area near the sea.
More than 350 pro-GNA fighters have been killed and nearly 2 000 wounded in the battle, according to medical sources. ISIS casualties figures are unavailable.
Sirte itself has been emptied of its residents, apart from families of ISIS militants, according to the pro-GNA forces.
Pentagon spokesperson Gordon Trowbridge in mid-August estimated that jihadist fighters in Sirte numbered fewer than 1 000.