riyadh saudi arabia say thursday dismantle islamic state cell capital riyadh connection plot launch suicide attack defense ministry two militants kill five others arrest raid three locations wednesday official source newly-created presidency state security say statement state-run television deadly bomb shoot attack mount islamic state militants security force shi ite muslims saudi arabia islamic state years criticize leadership western-allied kingdom world top oil exporter accuse deviate strict interpretation islam advance interest u.s. enemies thursday statement say suicide bomber eastern riyadh district al-rimal detonate vest security force surround house use manufacture suicide vest explosives another militant kill security force hole firearms apartment western district al-namar say third raid horse stable southern riyadh suburb al-ghanamia statement say use headquarter security force seize firearms bomb-making materials show state television along burn car damage build first militant blow suspect identify security force close several areas riyadh wednesday videos share online show plume smoke rise one location plot attack defense ministry uncover last month allegedly involve two yemeni nationals two saudi citizens saudi security source say time one detainees member arm houthi movement lock 2-1/2-year-old war saudi-led coalition yemen saudi arabia say dismantle islamic state cell riyadh