BASRA: A bomb attack on an Iraqi oil storage depot set one tank ablaze on Sunday in a rare assault on strategic southern oilfields, but the country's crude exports were unaffected, a top Iraqi oil official said. The attack underscored the complex task Iraq faces in protecting and building up its oil infrastructure as the last U.S. troops prepare to withdraw from the OPEC country at the end of the year when a bilateral security pact finishes. Dhiya Jaffar, head of the state-run South Oil Company, said the attack set ablaze one tank at the Zubair 1 storage facility, but the explosion had not affected pumping to Al Fao port, where crude exports are dispatched. “The fire is still burning, but it is under control. Production has been adjusted so daily production levels and export levels are not affected. Exports are continuing at the same rate,” Jaffar told Reuters. An Iraqi police source said bombs targeted four tanks at the facility, but only one of the tanks hit contained crude and ignited. Another bomb hit an empty tank and bombs at two other tanks were made safe, the police source said.