Forces loyal to Libya's UN-backed Government of National Accord stand in Sirte as they comb through some residential neighborhoods that were previously controlled by Islamic State. (Mahmud Turkia/AFP/Getty Images)

Lawmakers in Libya’s parliament refused to give their approval to the country’s U.N.-backed government Monday, delivering a fresh setback to efforts to stabilize a country fractured by conflict and wounded by a sinking economy.

The no-confidence vote against the Government of National Accord (GNA), which is based in the capital city of Tripoli, occurred in a rare session of the parliament, which is based in the eastern city of Tobruk. Of the 101 lawmakers who attended, 61 voted against the government, 39 abstained, and only one sided in favor, according to a statement on the parliament’s website.

The United States and other Western powers view the GNA as Libya’s best chance to fight a virulent Islamic State, resuscitate dwindling oil production and combat the human-trafficking networks behind the flow of migrants crossing the Mediterranean to Europe’s shores.

But even as pro-GNA militias are on the verge of driving out the Islamic State from its stronghold in the coastal city of Sirte with help of U.S. airstrikes, the government has been unable to extend its authority beyond Tripoli.

Monday’s vote triggered disputes between the supporters of Prime Minister Fayez al-Serraj and his opponents in the parliament over the legitimacy of the vote. Members of the pro-Serraj bloc claimed they were blindsided, saying the vote was not included in the parliamentary agenda on Monday. Many Serraj supporters did not attend the session.

“The vote can potentially throw the whole unity process up in the air,” said Mattia Toaldo, senior policy fellow at the European Council on Foreign Relations in London.

Libya plunged into chaos after the overthrow and killing of dictator Moammar Gaddafi five years ago. It has had rival governments , each supported by a meld of tribes and militias. Serraj’s unity government was set up in December under a U.N.-brokered agreement.

In the east, though, powerful figures remain opposed to Serraj and the GNA’s leadership committee. Monday’s session was chaired by the speaker, Agilah Saleh, who is allied with Gen. Khalifa Hifter, a military commander who controls large swaths of the east. Both have refused to back Serraj.

In January, the parliament rejected an initial list of ministers proposed by the GNA, and opposition lawmakers have continued to demand a shake-up in Serraj’s cabinet to include more eastern representation.

It’s unclear whether Monday’s vote would dissolve the unity government, and compel Serraj to replace some or all members of his cabinet. If it does, analysts say, Libya’s instability could deepen.

“The legitimacy of the vote could be questioned by some players,” Toaldo said. It could also take months, he added, to reach consensus on new cabinet nominations, and “in the meantime, violence could flare up again either in the oil installations east of Sirte or in and around the capital.”

“The only way out could be a stronger international mediation that avoids both a stalemate of the institutions and an escalation on the ground,” Toaldo added.