Militants in police uniforms claiming to be carrying out a security operation on Monday kidnapped and killed six men in a pre-dawn attack north of Baghdad, officials said.
The attack is the latest in spiralling violence across the country that has spurred concerns of a revival of the all-out sectarian bloodshed that left tens of thousands dead in 2006 and 2007.
Authorities have carried out wide-ranging operations against militant groups in recent weeks in a bid to combat the unrest, but analysts and diplomats say the government has not resolved the underlying causes of the violence.
On Monday, gunmen dressed in police uniforms stormed several houses in the predominantly Sunni town of Tarmiyah, just north of Baghdad, claiming to be carrying out a security operation, police and an interior ministry official said.
Signup to our newsletter and follow us on Facebook and Twitter!
They kidnapped six men and left the area.
Local residents found the bodies of the six men hours later just outside the neighbourhood, the security sources said. A medical source at the local hospital confirmed receiving the six bodies, all of which bore gunshot wounds.
Violence has increased markedly in Iraq this year.
Attacks have killed more than 3,600 people since the beginning of 2013, according to figures compiled by AFP.
Prime Minister Nuri al-Maliki has vowed to press on with an anti-militant campaign, but analysts say the authorities should focus on resolving anger in the Sunni Arab community over perceived ill-treatment by the Shiite-led authorities and security forces.