RIYADH (Reuters) – Top oil exporter Saudi Arabia has arrested scores of militants accused of plotting attacks on oil facilities, in one of the biggest swoops by the kingdom in several years, state media said on Wednesday.

Those arrested included about 50 Saudis and dozens from Yemen, which jumped to the forefront of Western security concerns after a failed December bombing on a U.S.-bound plane claimed by the Yemen-based regional al Qaeda wing, the media said.

The militants were organized in three cells, two of which were planning to attack oil and security facilities in the oil-producing Eastern Province. They included a Yemeni who security officials describe as being a prominent member of al Qaeda.

“We seized belts of explosives which they were planning to use in suicide attacks,” one security official said.

Most of the militants were arrested in the southern province of Jazan, near the border with Yemen. The dates of the arrests were not disclosed.

Islamist militants in 2003 launched a violent campaign to topple the U.S.-allied monarchy, killing nearly 200 people, including foreign residents.

But a security crackdown coupled with tighter controls on financing and the spread of militant ideas helped curb violence inside the kingdom after 2006.