Interior Ministry spokesman Brig Gen Saad Maan said the attacker detonated his bomb in the doorway of the mosque as worshippers were exiting after midday prayers. He confirmed the toll.
The IS group claimed the attack in a statement circulated online by its supporters. The claim bore the group's logo and resembled previous claims issued by the extremists. IS has repeatedly targeted Iraq's Shiite majority, who the Sunni extremists view as apostates.
Iraqi forces backed by US-led airstrikes have struggled to roll back the insurgents since they swept across large areas in the country's north and west in the summer of 2014.
