The bomber struck in the Shiite-majority Saadiyah area of confessionally mixed Diyala province, cutting through a massive security operation put in place for the climax of the Ashura festival, which has been hit repeatedly by Sunni militants in the past.
Another 65 people were wounded in the bombing, the officials said.
It was the third attack of the day to target Shiite devotees.
Earlier, coordinated blasts in the Hafriyah area, south of Baghdad, killed nine people, while twin bombings in the northern oil city of Kirkuk wounded five, police and medical sources said.
