The attack, which occurred on Wednesday 60 kilometers (37 miles) south of the northern city of Mosul, also wounded another two police.
The morning assault was followed by a roadside bomb exploding as emergency personnel travelled to the scene, wounding two more people.
In a separate incident, gunmen shot dead a man in Baquba, a city north of Baghdad.
The attacks came a day after 29 people were killed in violence in Iraq.
With the latest unrest, more than 640 people have been killed in attacks so far in July, making it the deadliest month in a year marked by spiraling violence.
More than 2,900 people have died in attacks so far this year, according to AFP figures based on security and medical sources.