Libya's interim General National Congress, officially replaced by a parliament elected in June, on Monday named pro-Islamist figure Omar al-Hassi to form a "salvation government", An-Nabaa television station reported, AFP reported.
The Islamist-dominated GNC convened in Tripoli following an appeal by Islamists groups which contest the legitimacy of the new parliament, based in the eastern city of Tobruk for security reasons.
An-Nabaa gave no figure for the number of GNC members who voted to appoint Hassi.
The television station said earlier that the meeting had failed to reach the quorum of 94, although other reports said that more members had arrived later.
Hassi is a lecturer in political science at the University of Benghazi in eastern Libya.
He was the losing candidate in a GNC election in June for a new prime minister.
Ahmed Miitig was elected instead, but the supreme court ruled the process was unconstitutional and Abdullah al-Thani remained interim premier.
Islamists called for the GNC to reconvene after they accused parliament of complicity in air raids last week on Islamists battling to capture Tripoli international airport from the nationalist Zintan militia.
The Islamists claimed to have seized the airport and television pictures on Monday showed them apparently running rampage and celebrating their capture of the facility.