Iraqi officials say they have found the bodies of 18 kidnapping victims north of Baghdad.
Reports said all the victims had been shot execution-style within hours of their capture. The group of corpses was found in farmland near the towns of Meshahda and Tarmiyah.
It was the deadliest in a series of execution-style killings which are on the rise in Iraq, alongside a growing insurgent campaign of bomb and gun attacks targeting security forces and civilians.
The victims were taken from their homes early on Friday by men wearing military uniforms and driving around six SUVs, the sources said. It was not clear who was behind the attack, but this area of Iraq has seen frequent abductions by militants dressed as soldiers.
The men's families went to local police to report their relatives missing and police later found their bodies in an orchard.
This year has been Iraq's most violent since 2006-7, when tens of thousands of people died at the height of sectarian strife between Sunnis and Shi'ites. In 2013, more than 200 people were killed in attacks in each of the first four months of the year.
On Wednesday, police found the bodies of 13 people around Baghdad, the apparent victims of execution-style shootings. It did not appear that Friday's killings were linked to those earlier in the week.
Among those killed on Friday were a police officer and an army official, the headmaster of a school and a mayor from the neighborhood. A Sunni Muslim tribal sheik and his son were also among those shot dead.
Some information in this report was contributed by Reuters.