A message posted on an al-Qaida terror web site claims responsibility for Friday's attempt to blow up the world's largest oil refinery, located in eastern Saudi Arabia.
The al-Qaida message -- which has not been authenticated -- calls the attack a success, and says bombers penetrated the security perimeter of the oil and gas refinery.
Saudi authorities said the attack was foiled when guards opened fire on two attack vehicles, causing them to explode. Two security officers and two attackers were reported killed. The Saudi oil minister says the explosion did not affect operations at the plant, which handles two-thirds of the Kingdom's oil output.
Oil prices jumped more than two dollars a barrel on news of the blast in Saudi Arabia, which is home to one-quarter of the world's proven oil reserves.