The bodies of 18 people kidnapped hours earlier by men in army uniforms were found abandoned north of Baghdad on Friday, the latest troubling sign of worsening violence in Iraq.
The killings come amid a surge in violence that has included multiple attacks with victims snatched from their homes, only for their corpses to be found later in scenes eerily recalling the worst of Iraq's gruesome 2006-07 sectarian war.
More than 6,000 people have been killed this year, forcing Baghdad to appeal for international help in battling militancy just months before a general election, as official concern focuses on a resurgent Al-Qaeda emboldened by the civil war raging in neighbouring Syria.
Early Friday, authorities discovered the bodies of 18 men, including two tribal chiefs, four policemen and an army major, dumped in farmland near the Sunni Arab town of Tarmiyah, just north of Baghdad.
All of the men had been shot in the head and chest, two police officers and a medical source said.
The kidnappers, wearing military uniform and travelling in what appeared to be army vehicles, had abducted the men in the early hours of Friday.
They told the victims' families that they were suspects in a variety of investigations who had to be taken away for questioning.
Their bodies were found hours later, the sources said.
The brutal killings come just days after authorities discovered the bodies of 19 people who had been shot dead in various parts of Baghdad, including eight who were found blindfolded and six whose corpses were left in a canal.
At the peak of Iraq's sectarian fighting in the wake of the 2003 US-led invasion, Sunni and Shiite militiamen would regularly carry out tit-for-tat kidnappings and assassinations and leave scores of corpses littering the streets.
Many of the bodies were blindfolded and showed signs of torture.
Elsewhere in Iraq on Friday, four people were killed and five others wounded in attacks in and around the restive mostly Sunni cities of Mosul and Baquba, officials said.
Baghdad and Sunni Arab parts of northern and western Iraq have borne the brunt of the recent upswing in bloodshed.
The violence worsened sharply after security forces stormed a Sunni protest camp in northern Iraq in April, sparking clashes in which dozens of people died.
The authorities have made some concessions aimed at placating the protesters and Sunnis in general.
These include freeing prisoners and raising the salaries of anti-Al-Qaeda Sahwa fighters, and the security forces have also trumpeted operations targeting militants.
But daily attacks have shown no sign of abating, with Friday's killings capping a week in which nearly 200 people have died nationwide.
More than 6,000 people have been killed so far this year, according to an AFP tally based on reports from security and medical officials.
Diplomats, analysts and rights groups say the government is not doing enough to address Sunni disquiet over what they see as mistreatment at the hands of the Shiite-led authorities.
On Wednesday, the UN Security Council condemned the violence and voiced support for government efforts to tackle the bloodshed.
"The members of the Security Council expressed their deep condolences to the families of the victims and reaffirmed their support for the people and the government of Iraq, and their commitment to Iraq's security," a statement said.
Prime Minister Nuri al-Maliki used a recent trip to Washington to push for greater intelligence sharing and the timely delivery of new weapons systems in a bid to combat militants.
Both France and Turkey have offered his government assistance.