Saudi Arabia will set up special security units to protect oil and industrial facilities against militant attacks, the Interior Minister said in remarks published on Monday.

Prince Nayef bin Abdul-Aziz also told members of the unelected Shura Council that the kingdom was holding more than 3,000 suspects, many linked to a campaign by al Qaeda launched in 2003 to overthrow the pro-Western royal family.

Saudi Arabia has said it foiled at least two major plots since 2006 to hit major oil facilities in the kingdom, the world's largest oil exporter.

Prince Nayef told the quasi-parliament on Sunday that preparations were being made to establish a force of 35,000 men to protect oil and industrial installations.

The comments were reported in Saudi media from a speech the senior member of the Saudi royal family gave to a closed Shura Council session.

Saudi Arabia holds 25 percent of the world's known reserves. It is striving to become one of the world's leading petrochemical manufacturers.

Security is already tight around oil installations, which are mostly in the Eastern Province near the Gulf coast.

Prince Nayef also said that of 9,000 suspected militants seized since 2003, 3,106 remain in detention. He said some of them would face trial, but gave no more details. Militants linked to al Qaeda launched a campaign to bring down the U.S.-allied royal family in 2003, targeting government buildings, energy industry facilities and foreign residential compounds.

In April, it said that more than 170 people were arrested for planning attacks on oil and industrial facilities, including some who had been training as pilots in preparation for possible suicide operations.

Five of the men played a role in an attempt to storm a major oil facility at Abqaiq in February 2006, a security source said. It was not clear why they were uncovered now.