At least 26 people have been killed in attacks in Iraq, 18 of them in seven car bombings in the capital.
The attacks were the latest in a surge of unrest that has left more than 4200 people dead this year.
Near the main northern city of Mosul, gunmen ambushed a vehicle carrying unarmed policemen and raked it with machine guns on Tuesday, the officials said.
Six policemen were killed in the attack and two seriously wounded.
In the evening, seven car bombs struck various parts of Baghdad, including the centre and the northeast, killing at least 18 people, most of them civilians, and wounding nearly 100.
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Earlier in the day, a provincial official was shot dead in Baghdad while a soldier was killed west of Mosul by an explosive device.
In Fallujah, west of the capital, militants wearing explosive belts attacked a police station and traded fire with security forces.
Three of the bombers were killed when their explosives blew up while a fourth suspect was shot by police, officials said, adding that 12 policemen were wounded.
