The Iraqi authorities have executed 13 prisoners accused of taking part in the insurgency.
The men after they apparently confessed to taking part in "crimes against Iraqis" in northern Iraq.
An Iraqi cabinet statement listed the name of only one of those hanged, Shukair Farid, a former policeman in the northern city of Mosul, who allegedly confessed that he had worked with Syrian foreign fighters to enlist fellow Iraqis to carry out assassinations against police and civilians.
"The competent authorities have today carried out the death sentences of 13 terrorists," the statement said.
It said Farid had "confessed that foreigners recruited him to spread the fear through killings and abductions."
In September, Iraq hanged three convicted murderers, the first executions since Saddam Hussein was deposed in 2003. They were convicted of killing three police officers, kidnapping and rape.
Iraqi authorities reinstated the death penalty after the end of the US-led occupation in June 2004 so they would have the option of executing Saddam if he is convicted of crimes committed by his regime.
He and seven co-defendants are on trial for allegedly massacring more than 140 people in Dujail, north of Baghdad, after an alleged assassination attempt against him in 1982.
Death sentences must be approved by the three-member presidential council headed by President Jalal Talabani, who opposes capital punishment. In the September executions and again in today's hangings, Talabani refused to sign the authorization himself but gave his two vice presidents the authority.
Meanwhile, a series of explosions, including a car bomb that struck a Sunni mosque, and a shooting killed 16 civilians and wounded 31 as a dust storm enveloped the capital.
In political developments, Shia politicians said they had asked Kurdish President Jalal Talabani to convene parliament March 19, one week past the constitutional deadline, marking an apparent compromise in the battle over a second term for Shia Prime Minister Ibrahim al-Jaafari.