Five people have been arrested in Saudi Arabia on suspicion of involvement in a foiled attack on an oil facility in February, police say.
Abqaiq is the world's biggest oil-processing plant
The militants were linked to the attack on the Abqaiq compound - the world's biggest oil-processing plant, said an interior ministry statement read on TV.
A tape showed the men allegedly preparing the cars used in the attack.
The tape and 1.5 tons of explosives were found in a warehouse outside the capital, Riyadh, the TV report said.
At the end of March, the authorities said they had arrested 40 suspected members of al-Qaeda, eight of whom were said to be linked to a cell that tried to bomb Abqaiq.
During the attack on the plant on 24 February, guards opened fire on at least two cars carrying explosives as they tried to ram the gates. Two guards were killed.
Three days later, security forces in Riyadh killed five suspected militants believed to be linked to the attack.
It was thought to be the first direct assault on Saudi oil production, almost certainly linked to al-Qaeda, said the BBC's security correspondent Frank Gardner.
For some months, al-Qaeda's leaders had been calling on their followers to attack oil installations, saying that the revenues from Muslim oil went to the enemies of Islam, our correspondent says.
Abqaiq handles about two-thirds of the country's production and is an important gathering point for crude oil coming in from several large oil fields.