The UN, together with the EU and United States have appealed for calm as tensions escalate between Libya's two executives.
Since the beginning of March that Libya has two rival governments.
The appeal follows an annoucement made by former interior minister Fathi Bachagha, approved by the parliament sitting in the east, that he would be heading to the capital.
The incumbent Tripoli cabinet, which emerged from UN-sponsored political agreements, is headed by outgoing prime-minister Abdelhamid Dbeibah who has so far refused to relinquish power.
On Thursday, images and videos of convoys of armed militia vehicles circulated on the social networks. The images suggest preparations for entry into the capital, Tripoli.
Many fear a return to the civil war that followed the overthrow of Muammar Gaddafi's regime in 2011.