Islamic State (IS) terrorist group threatened to carry out more attacks against Shiites in Saudi Arabia, Al Bawaba News reported Saturday. IS targeted May 29 a Shiite mosque, eastern Saudi Arabia, during Friday prayer, leaving four dead and seven injured, the second after an attack on another Shiite mosque in Al Qatif, leaving 21 dead and 81 injured. Amnesty International Organization urged the oil-rich kingdom to take serious measures against extremism as well as to provide enough protection for the Shiite minorities.