Protesters blocked the entrance to an oilfield belonging to Libya's Waha Oil, preventing contractors from working there, industry sources said, the latest disruption in the industry providing the lion's share of Libya's income.

The protest, which began on March 11, concerns demands that oil service contractors working at Waha's Gialo 59 field use local vehicles and drivers, one Libya oil source familiar with the matter said on Thursday.

"They weren't allowing trucks transporting equipment to go through, so this had an affect on drilling operations," the source said, adding the protesting group was from the town of Jalu some 30 kms (19 miles) away.

"They have been calling for local vehicles to be used."

A senior Libyan oil source said the protest was ended and that it had had an indirect impact on operations. He said the protesters had called for drivers working at the field to be part of a locally formed transport union.

In a series of incidents in recent months, activists and local militia have disrupted operations of Libya's energy sector in pursuit of goals such as better living conditions or more regional autonomy.

The disruptions have affected the OPEC member's return to production close to pre-war levels of 1.6 million barrels of oil per day (bpd), although that return has still been faster than expected. In July protesters forced the closure of three major oil terminals.

Waha is a joint venture between Libya's National Oil Corporation (NOC) and U.S. companies Marathon, Hess Corp and ConocoPhillips.

Waha officials have said it expects to nearly double oil output within five years to 600,000 bpd. The firm operates several fields including Waha, Dahra and Samah.