Production at Libya's giant Sharara oil field was expected to fall by at least 160,000 barrels per day (bpd) on Saturday after two staff were abducted in an attack by an unknown group, the National Oil Corporation (NOC) said.
The attack happened at a control station on the outskirts of Sharara, about 40 km (25 miles) from the main part of the field, engineers at the field said. One of the abducted workers was Romanian, they said.
NOC said it expected output to drop by 160,000 barrels per day (bpd), although one engineer said output at the field, which had been producing 200,000-300,000 bpd recently, had already dropped to below 100,000 bpd.
Tripoli-based NOC operates Sharara in partnership with Repsol, Total, OMV and Equinor , formerly known as Statoil.
The field, in Libya's remote southwest, has suffered security problems in the past, including raids in which vehicles and mobile phones have been stolen.
The facility that was targeted on Saturday is called Station 186 and was also attacked last year.
The NOC said unknown armed assailants entered the station at 6.30 a.m. (4.30 GMT) on Saturday.
"Four of the station staff were initially kidnapped but two of them have been since released," it said. "Oil wells in the surrounding area have been shut down as a precaution, and all other workers evacuated."
An engineer at the field said one of the abducted workers was Romanian.
In addition to being one of Libya's main export grades, Sharara feeds the 120,000 bpd Zawiya oil refinery on the country's northwest coast.