International efforts to install a unity government and end Libya's civil strife suffered a new blow overnight when an Islamist-leaning government that controlled the capital Tripoli until March attempted to regain power.
Khalifa Ghweil, who was prime minister in the unrecognized National Salvation Government, announced his administration's comeback from inside the headquarters of the former parliament after his militia supporters seized the building.
Ghweil, who has been sanctioned by the EU for obstructing the peace process, called on the internationally backed Presidency Council of Prime Minister Fayez Serraj to stop work.
He also called for a direct unity deal with a third rival administration in eastern Libya instead of the UN-backed peace deal that brought Serraj and his allies to Tripoli in March.
Serraj's Presidency Council denounced the move and said it had ordered the arrest of "those politicians who are attempting to create parallel institutions without any legal justification."
UN Libya envoy Martin Kobler also condemned what he described as "yesterday's attempt to seize" the headquarters of the former parliament.
The UN-backed Libyan political agreement "remains the only framework for a peaceful solution in Libya and I urge all political stakeholders to unify behind it," Kobler said.
Despite the developments, no clashes were reported in Tripoli and there were no unusual signs of tension on Saturday morning.
The overnight developments, which apparently followed a dispute over payment of wages to Serraj's presidential guard, were the latest in a series of setbacks for the nascent national unity government.
It was supposed to solve the split between Islamist-leaning factions that dominate western Libya and had backed Ghweil's government, and the centrists who dominate the elected parliament based in Tobruk in eastern Libya.
But Serraj's proposed government line-up was rejected in August by the Tobruk parliament. Then in September, forces loyal to Tobruk military chief Khalifa Haftar seized the country's key oil ports from an ally of Serraj.
Analyst Mattia Toaldo of the European Council on Foreign Relations recently wrote that those developments, and Haftar's growing military strength and popularity, meant that "the sky has fallen" on the UN-backed peace deal.
The priority for the international community should be finding a way to allow it to be renegotiated without fighting, Toaldo suggested.
Libya has suffered from political and security chaos since longtime dictator Moamer Gaddafi was overthrown and slain in a 2011 uprising.
Resolving its conflict became a priority for European and other powers when it emerged as a hub for people-smuggling across the Mediterranean and Islamic State carved out a territory on its central coast.
Militias aligned to Serraj's government have now forced the jihadis from most of that area and are attempting to recapture their last holdouts inside the central city of Sirte.