A suicide bomber killed 21 worshippers on Friday in a packed Shi'ite mosque in eastern Saudi Arabia, residents and the health minister said, the first attack in the kingdom to be claimed by Islamic State militants.
It was one of the deadliest assaults in recent years in the largest Gulf Arab country, where sectarian tensions have been aggravated by nearly two months of Saudi-led air strikes on Shi'ite Houthi rebels in neighboring Yemen.