An unnamed armed group shut a valve on a pipeline from Libya’s largest oil field, causing a drop in production, the National Oil Corporation (NOC) said late Monday.The disruption threatens production from the El Sharara field, a key source of crude for Libya, an OPEC member that holds Africa’s largest proven oil reserves.Armed groups and protesters frequently target oil fields, pipelines and export terminals to press political or economic demands.The NOC said in a statement that the closure affected a pipeline linking the El Sharara field, some 700 kilometres south of Tripoli, to the coastal city of Zawiya, home to one of the country’s main export terminals. It did not name the group responsible.If the shutdown continues, the company could be “compelled to declare force majeure”, a legal provision that allows suppliers to suspend contractual obligations because of circumstances beyond their control. The NOC declared force majeure at El Sharara in January 2024 during a previous closure.”The closure caused a pressure buildup within the crude oil pipeline, leading to a significant reduction in production at the El Sharara field,” the NOC said in a statement.Such a scenario would directly reduce state revenues at a time when global oil prices are rising, it added. Oil prices have risen above $100 a barrel in recent weeks amid disruptions to Gulf shipping linked to the Iran war.The company also warned that the Zawiya refinery, about 45 kilometres west of Tripoli, could be forced to shut down if the disruption continued.Despite its vast energy wealth, Libya has been beset by violence and instability since the overthrow of Muammar Gaddafi in 2011.It remains divided between the UN-recognised government in Tripoli led by Prime Minister Abdulhamid Dbeibah, and the rival administration in the east backed by military strongman General Khalifa Haftar.El Sharara is Libya’s largest oil field operated by Akakus Oil Operations, a joint venture of the NOC alongside Spain’s Repsol, France’s TotalEnergies, Austria’s OMV and Norway’s Equinor.At full capacity it produces approximately 350,000 barrels per day, accounting for roughly a third of Libya’s total output.It was shut for two years between November 2014 and December 2016 after a pipeline blockade by armed groups, and has suffered repeated stoppages since Gaddafi’s overthrow.