Iraqi officials are investigating a series of attacks that have killed at least 29 people, including the abduction and murders of 18 people in a predominately Sunni region.
Investigators found the bullet-ridden bodies of the 18 kidnapping victims on Friday in a farming region near Baghdad.
The victims include several security officers and at least one tribal chief.
Investigators say unidentified gunmen posing as security officers kidnapped the men from their homes late Thursday and early Friday.
Their murders are the latest in a series of execution-style killings in the country.
Violence in Iraq has fallen from its peak in 2006 and 2007, but attacks across the country remain common.
Iraq Body Count, a group that tracks civilian casualties, says more than 800 civilians have been killed so far this month and about 8,000 since January.
In other incidents Friday, a bombing at a football field west of Baghdad left five people dead.
Also, police say six women were shot and killed in a house in the capital.