Leaders of Libya’s new unity government have arrived in the capital, Tripoli, by boat in an attempt to take control.
Over recent days, Tripoli’s airspace has been intermittently closed to stop the Presidency Council, which has been based in Tunisia, from arriving by air.
Libya’s UN envoy called for a “a peaceful and orderly handover”.
But hardliners in the coalition that controls Tripoli are opposed to the UN-brokered deal aimed at reconciling a nation split by five years of conflict.
Libya has been in chaos since the 2011 overthrow of long-serving ruler Muammar Gaddafi by Nato-backed forces.
From 2014 it has had two competing administrations, one in Tripoli – backed by powerful militias – and the other about 1,000km (620 miles) away in the port city of Tobruk.
In December, some of these rival lawmakers signed up to the UN agreement to form a unity government, but the deal has not yet been backed by all the country’s many militia brigades that were formed in the wake of the uprising.
The agreement saw the formation of a nine-member Presidency Council, which includes the unity Prime Minister Fayez Sarraj who arrived with some of his deputies at a naval base in Tripoli on Wednesday.
The BBC’s North Africa correspondent Rana Jawad says the Presidency Council has faced numerous challenges since its formation, chief of which has been its inability to establish a presence in Tripoli.
It also proposed a unity cabinet over a month ago, but the Libyan parliament in Tobruk has so far failed to reach a quorum to vote on it, she says.
UN envoy Martin Kobler said the politicians’ arrival in Tripoli – after at least two failed attempts to fly in – marked “an important step in Libya’s democratic transition and path to peace, security and prosperity”.
In a statement, he “urged all public bodies, including official financial institutions, to facilitate an immediate, orderly and peaceful handover of power”.
European Union foreign policy chief Federica Mogherini added: “The arrival of the Presidency Council in the capital represents a unique opportunity for Libyans from all factions to reunite and reconcile.”
But our reporter says it is not clear how Mr Sarraj and his colleagues will be able to take over state institutions in Tripoli as they face stiff rivalry, including from militias, and members of his proposed cabinet are based all over the country.
Overnight, there were loud explosions and heavy gunfire in the city, Reuters news agency reports.
The cause of the firing was not immediately clear, but Tripoli has been on edge amid the reported attempts of the unity government leaders to land, it says.
A colonel at the navy base told the BBC a special security committee for the Presidency Council was responsible for arranging the trip of Mr Sarraj and his colleagues – and it was responsible for their safety.
The political and security vacuum in Libya has helped the so-called Islamic State group to establish a foothold in the north African country, carrying out attacks on cities and against oil installations.
