Unknown attackers blew up Yemen’s main oil export pipeline in the central province of Ma’rib, halting the flow of crude oil, government and industry sources said. Yemen’s Defence Ministry said in a statement on Friday that the pipeline in Serwah was exploded by “subversive elements.” Local sources told Arabstoday that clashes broke out following the attack between armed forces and a protection brigade that accompanied the engineers repairing the pipes. Oil revenues make up more than 70 per cent of the state budget, with oil and gas products accounting for over 90 per cent of Yemen\'s exports. Insurgents and tribesmen have repeatedly attacked oil and gas pipelines in Yemen over the past two years in a bid to win concessions from the central government, causing fuel shortages and slashing export earnings in the impoverished country.