Sana’a, Reuters—Yemeni tribesmen bombed Yemen’s main crude export pipeline on Saturday, forcing oil flows to be stopped, industry sources told Reuters.

Yemen’s oil and gas pipelines have repeatedly been sabotaged by insurgents or angry tribesmen since anti-government protests created a power vacuum in 2011, causing fuel shortages and slashing export earnings for the impoverished country.

Its main export pipeline carries around 70,000 to 110,000 barrels per day of Marib light crude to an export terminal on the Red Sea.

“The pipeline was attacked by tribesmen. The damage is quite big and oil flow has stopped,” said an industry source, declining to be identified.

A long closure in 2011 forced Yemen’s largest refinery at Aden to shut, leaving the small producer dependent on fuel donations from Saudi Arabia and imports.

The demands of the tribesmen were not known, but in the past they have wanted relatives to be released from prisons or to protest against their unemployment.

Yemen’s stability is a priority for the United States and its Gulf Arab allies because of its strategic position and proximity to key shipping lanes, and because it is home to one of the most active wings of Al-Qaeda.