Eastern Libyan forces loyal to Libyan commander Khalifa Haftar captured the closed El Sharara oilfield on Wednesday, officials said in a challenge to the Tripoli government, Reuters reports.
El Sharara was taken over on Dec. 8 by groups of tribesmen, armed protesters and state guards demanding salary payments and development funds.
But some tribesmen demanding development funds remained at the 315,000 barrel-per-day oilfield, one of their protest leaders told Reuters.
Haftar's Libyan National Army (LNA) group, which is based in the east, called oil firm NOC to lift force majeure, a contractual waiver, it had declared when it shut down production.
NOC declined to comment.
The LNA said it had met no resistance. "Our forces arrived safely at the field," a spokesman for the forces, Ahmed Mismari, told a news conference in Benghazi, where the LNA is headquartered.
A tribal protest leader told Reuters: "With the army (LNA) we can find an understanding as they are military people." He did not elaborate and it was impossible to get more details.
Libya's oil industry has faced disruption since the unrest began, with rival power centres in the west and east. Protesters and armed groups have often targeted oilfields and energy infrastructure.
Haftar is a dominant figure in the east where his LNA seized the second-largest city of Benghazi in 2017 by expelling Islamist and other fighters.
Last month, his forces started an offensive in the south to fight militants and secure its oilfields, and on Wednesday made good on the promise by moving on the El Sharara field.
A video posted online showed jubilant soldiers at the oilfield which is located deep in Libya's south and had previously belonged to the Tripoli-based internationally recognised government.
A resident confirmed LNA soldiers were inside the oilfield, a vast complex stretching for kilometres.
A Tripoli official, asking not to be named, acknowledged that the LNA was holding El Sharara. He declined further comment and there was no statement from the Tripoli government.
Tripoli had earlier on Wednesday appointed a military commander for the main southern city of Sabha and there were unconfirmed reports that Tripoli would dispatch a force to secure El Sharara.
Haftar's forces are allied to a parallel administration based in eastern Libya. His LNA faction last month started a military offensive in eastern Libya to fight militants and secure the region's oilfields.
An executive at NOC unit AGOCO, citing OMV, said on Twitter the El Sharara oilfield could reopen in March. NOC operates Sharara in partnership with Repsol, Total, OMV and Equinor.
A NOC board member, Jadalla al-Awkaly, praised the LNA advance, writing on his personal Facebook page: "A national army with a pure desire to liberate the homeland."
NOC is based in the capital Tripoli, in the country's west.