Production at the eastern Libyan oilfields of Misla, Sarir and Nafoora has been cut by more than half, and the fields are being jointly secured by workers and the army, an oilfield manager said on Saturday.
Many of Libya's key oil producing areas and terminals are located in the east of the OPEC member state, large chunks of which have fallen to rebels seeking to oust veteran leader Muammar Gaddafi.
"We have cut production to a minimum, well below half our normal production of 100,000 barrels a day, although I cannot give more details for security reasons," said an oilfield manager called Hossam, who works at Misla oilfield 400 km (250 miles) south of Benghazi.
He declined to give his full name.
"Two other fields nearby, Sarir and Nafoora, have done the same," he told Reuters by telephone.
Hossam said there were no security problems at any of the fields. "We are working as one team, one Libyan people, the workers and the army, to secure the oilfields and the infrastructure," he said.
Hossam said oil from Misla was going to terminals in Ras Lanuf and Tobruk and was being stocked there.
"We will be able to return to normal production immediately when the opportunity comes," he said.
Oil industry sources outside Libya say crude oil shipments from Libya, the world's 12th largest exporter, have almost halted because of reduced production, a lack of staff at ports and security concerns.
Libya normally produces about 1.6 million bpd of high-quality oil, or almost 2 percent of world output. Between 30 percent and 75 percent of output has been shut down due to the turmoil in the country.