The two parallel assemblies, each loosely allied with rival militias battling in Tripoli and elsewhere, are further fragmenting the vast, oil-rich country in the wake of the 2011 uprising that toppled longtime dictator Moammar Gadhafi.
The last four months have seen a renegade general battle Islamic militants in the eastern city of Benghazi, cradle of the 2011 uprising and powerful regional militias fight for control of the international airport in Tripoli.
Islamist-allied militias have seized virtually all of the capital.
The Islamist-dominated parliament in Tripoli today swore in Prime Minister Omar al-Hassi and 10 of his ministers, including the foreign, justice and oil ministers. Nine ministers have yet to be named. The body was replaced in June elections but it still convenes and refuses to recognize the new parliament, now based in the eastern city of Tobruk.
The newly-elected parliament is due to swear in a new government tomorrow. It is headed by the previous prime minister Abdullal al-Thinni.