A militia based in Libya’s western region has closed off pipelines running from three key oil fields to a refinery, causing a halt to production and dealing a further blow to the North African country’s desperate attempts to restore the critical flow.

The state-owned National Oil Company (NOC) said on Wednesday that the “criminal” armed group had in the past few days shut off two pipelines from the Al-Sharara and Al-Hamada oil fields to the refinery and port in Zawya.

The NOC said in its statement that militants had already halted the flow on Saturday from the Al-Fil field, another major oil field located west of Libya. It added that the stoppage had led to a reduction of 360,000 barrels per day (bpd) in Libya’s output, which was nearly one million bpd before the militants seized the pipelines.

Authorities declared force majeure at the three oil fields, meaning that the NOC could be exonerated from fulfilling oil contracts due to unforeseeable circumstances.

Sources in the area said the militia, which has yet to be named, was unhappy with what it described as the “marginalization” of the region.

Sitting on the largest oil reserves in Africa, Libya used to produce some 1.6 million bpd before the ouster and killing of strongman Muammar Gaddafi in 2011. The war between various militant groups caused a serious reduction in the output but a unity government established two years ago, which enjoys international backing but lacks consensus among some powerful domestic groups, has managed to repair the badly-needed export.

Western governments, which once supported a limited military intervention to topple Gaddafi, have failed in their efforts to establish peace and order in Libya as fierce fighting continues between militants loyal to rival administrations in the east and west of the country while other armed groups also vie for local power.

Estimates by the NOC say Libya has lost about 130 billion dollars in revenues since late 2014.