Saudi Arabia - Midday Prayer suicide bombing 21 killed 120 injured - Shiite Mosque - May 22, 2015

suicide bombing during midday prayer at a Shiite mosque in eastern Saudi Arabia. The Saudi Health Ministry said at least 21 people had been killed and more than 120 others injured.
It appeared to be the first official claim of an attack inside the kingdom by the Islamic State, which has seized control of much of Syria and Iraq.
The attack was a sign that Saudi Arabia’s intervention in the sectarian conflict in Yemen may be escalating tensions at home. Members of the Shiite minority in Saudi Arabia, who make up about 15 percent of the population and live mainly in the Eastern Province, have long complained of insults and discrimination by Saudi Arabia’s Sunni majority and its clerical establishment.
During Saudi Arabia’s two-month air campaign against the Houthi movement in Yemen, which practices a form of Shiite Islam and receives backing from Saudi Arabia’s regional rival, Iran, imams at Sunni mosques and commentators in the Saudi news media have frequently rallied the public around the war by denouncing Shiites as dangerous infidels.
http://www.nytimes.com/2015/05/23/world/middleeast/suicide-bombing-saudi-arabia-shiites-sunnis-yemen-mosque.html