Saudi Arabia said it had foiled an Islamic State plot to bomb its defense ministry headquarters and also said it had arrested several people suspected of carrying out espionage in the kingdom on behalf of foreign powers.

Saudi Arabia has previously been hit by deadly bombing and shooting attacks by Islamic state militants targeting security forces and Shi’ite Muslims.

The assailants were training in the use of explosive belts, the security source added, while authorities said they seized grenades and firearms during the operation to foil the attack.

Saudi State Television reported the arrests alongside footage of the explosive materials said to have been seized at the location the suspects were operating in.