Police said the bomb exploded in Kirkuk as worshippers were leaving after morning prayers marking the major Muslim holiday of Eid al-Adha, Voice of America reported.
Police said the explosion also damaged nearby cars and houses, China's state-run news agency Xinhua reported.
No group has claimed responsibility for the attack.
On Monday, U.N. Secretary-General Ban Ki-moon issued a statement condemning a series of bombings in the days leading to Eid al-Adha, calling them "particularly despicable" because they occurred as Iraqis observe the holiday by helping the needy and suffering.
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