A police officer said the attacker blew up his explosives-laden vest as people were leaving the al-Khairat mosque in Baghdad’s Sinak commercial area following noon prayers on Monday.
He said at least 25 people were wounded in the explosion.
The attack comes a day after a suicide bombing targeted a Shia mosque in the capital’s western Harithiya neighbourhood, killing 28 worshippers.
A medical official confirmed the casualty figures. Both officials spoke on condition of anonymity as they were not authorised to talk to media.