SANAA (Reuters) - Unidentified attackers blew up Yemen's main oil pipeline, forcing the country to shut down one of its most lucrative sources of income, government and tribal sources said on Saturday.

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

Witnesses said the pipeline linking production fields in the central Maarib province to the Red Sea was attacked on Friday night.

"We heard a blast in the Sirwah area followed by flames rising from the pipeline," one tribal witness told Reuters.

Yemen's stability is a priority for the United States and its Gulf Arab allies because of the country's strategic position next to top oil exporter Saudi Arabia and shipping lanes, and because is home to one of al Qaeda's most active wings.

A government source said production was halted after a device placed under the pipeline exploded.

"The army is on the trail of the saboteurs and technical teams will immediately start repairing the damage," the source said.

A long closure of the line last year forced the country's largest refinery at Aden to shut, leaving the small producer dependent on fuel donations from Saudi Arabia and imports.

On December 31, Yemen resumed oil pumping at a rate of around 70,000 barrels per day (bpd) after the latest repairs to a pipeline which used to carry around 110,000 bpd of Marib light crude to an export terminal on the Red Sea before a spate of attacks began in 2011.

(Reporting by Mohammed Ghobari; Writing by Sami Aboudi; Editing by Andrew Heavens)

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