The Saudi interior ministry said security guards were able to foil the attack after two cars attempted to breach the entrance of the Saudi Aramco-owned processing plant in Abqaiq, located in the oil-rich Eastern Province.
“Security men became suspicious of the two cars and exchanged fire with them. (The vehicles) exploded near the entrance and damage was limited to a small fire which was brought under control … Production operations were not affected,” the ministry said in a statement carried by the official SPA news agency.
The statement said that at least two of the would-be attackers were killed and two security guards were seriously wounded in the shoot out.
An official, who wished to remain anonymous, told AFP that the seriously injured security guards later succumbed to their wounds.
Six other Saudi Aramco workers “sustained slight wounds from shrapnel”.
It’s unknown exactly how many would-be attackers were in the vehicles but have sources said that some of the men wore uniforms of the state oil giant and used cars painted in the company’s colors.
The oil plant accounts for 70 percent of the kingdom’s production.
Wave of Al-Qaeda violence
It’s the first known attempted attack on an oil installation in Saudi Arabia a spate of violence erupted in May 2003 suspected to be perpetrated by Al-Qaeda militants.
Official figures show at least 90 civilians, 52 security personnel and 123 militants have died since the unrest began with hundreds more wounded. In response Saudi security officials have launched a major crackdown against suspected extremists.
In December 2004, Al-Qaeda chief Osama bin Laden called on his followers to target oil installations in both the Gulf and Iraq.
Saudi Oil Minister Ali al-Nuaimi, stressed that the output of the number one crude exporter had been unaffected.
“The plant continued producing at full capacity and export operations are continuing as usual,” Mr Nuaimi.
But world oil prices closed more than two dollars higher on news of the attempted attack with crude oil futures having jumped as much as three percent.
Saudi Arabia pumps around 9.5 million barrels of oil per day and sits on a quarter of the global oil reserves. According to a Saudi security expert, last September the kingdom increased spending on security of its oil industry to as much as $US1.5 billion a year.