Oil production has been suspended for several days at three oil fields in Libya after an armed militia shut off pipelines, the state-owned National Oil Company said Wednesday.
The output of oil, nearly one million barrels per day prior to the stoppage, had fallen by more than 360,000 bpd, NOC said in a statement.
The armed group, described as "criminal" by the company, had in the past few days closed off two pipelines to the refinery and port at Zawya from the Al-Sharara and Al-Hamada oil fields.
It had already blocked production on Saturday at the Al-Fil field, also located in the west of the country, said the statement from NOC.
The militia seized the pipelines to protest against the "marginalisation" of the region, according to sources in the area.
As a result of its actions, NOC said it had declared force majeure at the three affected oil fields.
The legal measure means that due to unforceable circumstances the company can be exonerated from fulfilling oil contracts.
Libya, which has Africa's largest oil reserves, used to produce about 1.6 million barrels per day before the 2011 armed uprising that toppled and killed dictator Moamer Kadhafi.
But it has only managed to export a few tankers of crude in recent months, with efforts to revive the industry thwarted by jihadist attacks and political turmoil.
The closure of oil ports has cost the country more than 130 billion dollars since late 2014, according to NOC.