BENGHAZI, Libya (AP) -- Libya's major oil fields and production facilities remained closed on Monday, its national oil company said, in a sign that the country's east-based forces are not backing down after an international summit to end the Libyan civil war.
The Libyan National Oil Corporation confirmed it had invoked force majeure on oil exports from two key southern fields, a clause that allows for a failure to fulfill international contracts due to a sudden disruptive event.
The continued closure of virtually all of Libya's oil facilities by eastern Libyan forces ratchets up pressure on their adversaries in the west, the U.N.-backed government that controls the capital, Tripoli.
World powers with interests in Libya's long-running conflict pledged on Sunday to respect a much-violated arms embargo and push opposing factions to reach a truce.
But on the ground, tensions remained high. As world leaders convened about military de-escalation, observers said scattered clashes erupted outside Tripoli, testing a tenuous week-old cease-fire.
Former general Khalifa Hifter's east-based forces have been laying siege to the capital for months.
"People are holding their breath," said Mohamed Eljarh, a political analyst who is based in the eastern city of Tobruk.
"I am worried there is no appetite among the warring parties and their constituencies for a truce right now," Eljarh added.
A doctor and resident of southern Tripoli, Mohamed Malek, 27, said he fled his neighborhood late Sunday when he heard sporadic exchanges of gunfire.
Another Tripoli resident, Ahmed Werfali, 34, said he heard a loud explosion early Monday, and limited fighting overnight. But the violence was far less than the routine pounding of heavy weaponry before the cease-fire, he said.
Aid workers in the capital's southern suburbs said they had not been able to recover corpses for several days because of continued fighting.
"We found six corpses stuck under rubble but there was intense shooting and we couldn't reach them until today," said Assad Jaafar, a spokesman for Libya's Red Crescent.
Dozens of men from tribal groups loyal to Hifter continued on Monday to camp out in the two southern oil fields, al-Sharara, Libya's largest, and al-Feel.
Hifter's tribal allies closed a major pipeline over the weekend, stopping about 380,000 barrels per day of production and potentially cutting national output to a small fraction of its normal level.
"This sit-in will continue," vowed Mohamed Maikal, the leader of the group that seized the fields, known as Fezzan. "There is a pessimistic situation after what happened in Berlin."
The protesters accuse the Tripoli-based government, which controls Libya's Central Bank, of using oil revenues to fund military operations against Hifter's forces.
The shut-down of production in the south follows the weekend closure of all eastern export terminals. Only offshore fields and one smaller facility remain operational, the national oil company said.
Oil, the lifeline of Libya's economy, has long been a key factor in the civil war, as rival authorities jostle for control of oil fields and state revenue. Libya has the ninth largest known oil reserves in the world and the biggest oil reserves in Africa.
It remains unclear whether the commitment to halt foreign interference announced in Berlin will prove any more effective in winding down the years-long war in Libya than past pledges that have been widely ignored.
Jalel Harchaoui, a Libya expert at The Netherlands Institute of International Relations, said that the Berlin summit had delivered "absolutely none" of the "concrete mechanisms" needed to ensure all parties to the conflict observe commitments to a truce and de-escalation.
Libya's two main rival leaders, Prime Minister Fayez Sarraj and former general Hifter, did not sign any documents, let alone appear in the same room. German Chancellor Angela Merkel and her foreign minister said they met the leaders separately ahead of the conference.
Turkish President Recep Tayyip Erdogan, speaking to reporters on his way back from Berlin, criticized Hifter's failure to ink a roadmap for ending the war. "It remained verbal, witnessed by those who participated in the meeting," the state-run Anadolu Agency quoted him as saying.
Germany's U.N. Ambassador Christoph Heusgen told reporters Monday the most important issue now is that the warring Libyan parties negotiate a "real cease-fire." Talks are supposed to start this week under U.N. auspices in Geneva, he said.
"What is very important is that everybody recognized there is no military solution to this conflict," Heusgen said.