Some were released later, but Saudi authorities say 520 people, including militants from north Africa, Asia, Afghanistan and Iraq, are still in custody.
The Saudi statement says terrorists were planning car-bomb explosions and attacks on security forces in a campaign to cripple the kingdom's oil industry.
Few details were released, but Saudi television showed a cache of weapons recovered from a desert hiding place.
Authorities say security forces seized arms, ammunition and cash and also recovered a message from Osama bin Laden's top deputy in al-Qaeda, Ayman al-Zawahri, encouraging terrorist recruits in Saudi Arabia and promising to send more fighters to join them from abroad.
The recorded message was seized during the arrest of a leader of an al-Qaida cell in Saudi Arabia's oil-rich Eastern Province.
Saudi Arabia is the birthplace of al-Qaeda leader Osama bin Laden, who is believed to be in hiding in South Asia.




