Iraqi gunmen have killed 25 people believed to be linked to Sunni militias opposing al-Qaeda, police say.Five women were among those killed, as the gunmen in army uniforms pulled the victims out of their houses in a village south of Baghdad on Saturday.
The victims were reported to have been tied up before being shot in the head.
Sunni militias turned against al-Qaeda and its militant allies two years ago in what was a key turning point in the campaign to quell the Iraqi insurgency.
Baghdad security spokesman Maj Gen Qassim al-Moussawi said police found seven survivors handcuffed in the same area.
"Also we confiscated the vehicle which was used in this attack," he said.
Local resident Muhammad Mubarak described what happened as "a tragedy".
"A group wearing National Guard uniforms and carrying night vision equipment stormed the homes of the victims and took them to their front gardens," he said.
"Then they handcuffed them with plastic tape and shot them in the head with guns fitted with silencers."
Mohammad al-Askari, of the defence ministry, said 24 people had been arrested from another Sunni village nearby with links to al-Qaeda.
"According to our investigation the perpetrators came from a village around 500m away.
"They are from the same tribe. They were around 25 armed men, wearing military uniform.
"One of them could say a few words in English to give the impression that this was a joint Iraqi-American patrol.
"They had with them a list of names, they knocked at the door, called out a name, then took the man or the woman who came out to a grove and killed them."
He added: "Our investigation has shown that they came from a village loyal to al-Qaeda network."
Insurgent stronghold
The village of Sufiya where the attack happened lies in a mainly Sunni area that used to be an insurgent stronghold.
In the past two years there have been many attacks aimed at punishing or intimidating Sunnis, but this is one of the bloodiest for some time, says the BBC's Jim Muir in Baghdad.
It shows that al-Qaeda or its allies are still in business, though much less effective than in the past, he adds, and there is no evidence they are regaining hearts and minds within the Sunni community.
The Sunni militias that lent their support to the government are known as Awakening Councils, or the Sons of Iraq.
US authorities set up the militias, paying, arming and training their members before Iraqi authorities took control of them in late 2008.
