Saudi Arabia says it has arrested 208 militants for involvement in cells planning an imminent attack on an oil installation, as well as attacks on clerics and security forces.

State television in the world’s biggest oil exporter said one of the cells was planning to smuggle in missiles. Al Qaeda sympathizers have mounted a campaign against the U.S.-allied monarchy since 2003.

A cell of eight militants led by a foreign resident planned an attack on an oil facility in the Eastern Province, it said. Saudi Arabia has been building a 35,000-strong rapid reaction force to protect installations after a failed al Qaeda attack in 2006 on the world’s largest oil processing plant at Abqaiq.

“Security forces foiled an imminent attack on an oil support installation in the Eastern Province after the perpetrators prepared themselves and set a date,” it said.

The report, citing an Interior Ministry statement, said 18 of those arrested belonged to a cell led by an “expert in launching missiles” who had slipped into the country. It said they planned to smuggle eight projectiles into the kingdom.