Protests have forced a major oil port in eastern Libya to shut down its operations for a fourth day, the deputy oil minister said on Wednesday.

Al-Zuweitina Oil port, 790 km east of Tripoli, receives oil pumped from at least three oil fields in the Libyan desert and is responsible for exporting 60 to 70 barrels of oil a day.

Omar Shakmak said protesters forced their way into the port's management offices on Saturday and ordered the port director to quit working and shut down operations.

"They want the government to provide them with jobs and believe they can put pressure on the government by stalling oil-related companies," he said.

A number of protests outside refineries and oil-related installations have posed a significant challenge to Libya's new government, which is dependent on oil for most of its revenue.

The administration is still struggling to impose order on a vast and divided country awash with arms and militias after the overthrow of Muammar Gaddafi last year.

Western Libya's main oil refinery has seen at least four shut downs since October causing petrol shortages in the capital Tripoli after war veterans demonstrating for more government compensation forced the refinery to shut down operations.