An explosion occured Friday at a major oil refinery in Buqayq, eastern Saudi Arabia, a Saudi oil official said. A pipeline was damaged in an attack on the refinery, Al-Arabiya TV reported. The explosion was caused by a vehicle packed with explosives that was detonated by the shots of security guards who fired on it as it tried to drive into the refinery, a reporter for the pan-Arab satellite channel Al-Arabiya said. There was no immediate confirmation of the report from the Saudi authorities. The guards managed to stop a second vehicle at the refinery's gates, the reporter said. Two assailants were killed in the attempt to break into the oil complex at Buqayq, which lies 70 kilometers southwest of Dammam. No guards were wounded, the reporter said.