Armed tribesmen bombed Yemen’s main oil pipeline on Saturday, halting crude flow to the country’s main export terminal less than a month after it was repaired, oil and local officials said. The attack occurred in the Serwah district in the central oil-producing province of Maarib, they said, and caused a huge fire that prompted the closure of the pipeline and stopped oil flow from the Maarib fields to the Ras Isa oil terminal on the Red Sea. Yemen, which relies on crude exports to finance up to 70 percent of its budget, has suffered frequent bombings of its main pipeline in recent years. The last one took place on Dec. 26 and the pipeline was repaired on Jan. 5.