Libya's National Oil Corporation and Central Bank, backbones of its wealth, have thrown their support behind a UN-backed unity government in a blow to a rival administration refusing to cede power.

Prime minister-designate Fayez al-Sarraj and members of the GNA arrived Wednesday in Tripoli where a rival government, unrecognised by the international community, has ruled since mid-2014.

The Central Bank of Libya also "welcomed" the GNA and wished them "all the success in carrying out the difficult tasks ahead of them".

It urged Libyans to "now more than ever to unite and collaborate by working together to ensure that security and safety prevail in Libya, to stop fighting and bloodshed, to empower the judicial system and to embrace the rule of law".