The forces of eastern Libya's military strongman Khalifa Haftar have lost control of a key oil export terminal they had seized last year, a spokesman conceded on Saturday.

Colonel Ahmad al-Mismari said that the rival forces had overrun the main airfield in the oil port of Ras Lanuf and identified them as Islamists of the Benghazi Defence Brigades.

An array of forces, most of them loyal to the UN-backed government in Tripoli, have been involved in efforts to oust Haftar from the oil ports, whose seizure enabled him to pose a major challenge to its authority.