Libya has begun importing diesel and fuel oil to keep power plants operating after protests closed most of the gas fields in its eastern region which usually supply them, an industry executive said on Monday.

No end is in sight to the worst disruption to Libya's oil industry since the civil war in 2011 as armed groups, security guards and oil workers with tribal loyalties shut down pipelines and oil ports across the country.

A National Oil Company senior official said Libya had imported at "least three times the quantities of liquid fuel" than usual in order to keep power plants operating.

"All the gas in the eastern part has stopped," said the official, who requested anonymity.

The official said that a vessel that had loaded 600,000 tonnes of crude from Brega port, which shipping sources said was the Eagle Trenton, had been asked by NOC to go to Zawiya port in the west because it was needed to supply its 120,000 bpd refinery, the biggest near the capital Tripoli.

The official said the Wafa gas field which produces around 13 million cubic metres per day in a joint venture with Eni was providing some relief for Libyan power plants that run on gas.

"We told the customer we cannot deliver the cargo because we needed it for domestic consumption," the official added. – Reuters