Libya's National Oil Corporation (NOC) declared force majeure on the Sharara oil field on 9 June, just three days after it restarted production.
A press statement from Libya NOC said an armed group stormed the field and coerced civilian workers to stop prorduction at the field.
"This criminal group dared to enter the field with heavy weapons," NOC chairman Mustafa Sanalla said. "It is clear that this criminal group places the interests of its commanders and the interests of the foreign powers tampering in Libya above the interest of the country.
"Instead of defending the country's interest and protecting civilians, the members of this armed group have directed weapons against our loyal Libyan workers who are making tremendous efforts to try to prevent Libya from resorting to banks to borrow to feed its people."