Iraq forces 'killed 255 Sunni prisoners' - HRW
Iraqi security forces and government-affiliated militias appear to have executed at least 255 prisoners since 9 June, a human rights group says.
The killings appeared to be retaliation for attacks by the jihadist Islamic State in Iraq and the Levant (Isis), Human Rights Watch (HRW) said.
The prisoners were all Sunni Muslims, while the majority of security forces and militia were Shia, they added.
An Iraqi military official denied any prisoners had been executed.
However, some prisoners may have died "as a result of terrorist acts", Lt Gen Qassim Atta, the military spokesman for Iraqi Prime Minister Nouri Maliki, said.
The number of those killed was lower than that cited in the report, he added, saying that a committee had been formed to look into the deaths.
Most of the executions took place as Iraqi forces fled advancing Isis fighters, HRW said in a statement.
The killings were reported in six Iraqi villages: Mosul, Tal Afar, Baquba, Jumarkhe, Rawa and Hilla.
"The mass extrajudicial killings may be evidence of war crimes or crimes against humanity, and appear to be revenge killings for atrocities by Isis," the statement said.
Last month, Isis insurgents seized huge swathes of north-western Iraq. The group has gained a reputation for brutal rule in the areas that it controls.
Joe Stork, HRW's deputy Middle East director, said: "While the world rightly denounces the atrocious acts of Isis, it should not turn a blind eye to sectarian killing sprees by government and pro-government forces."
The HRW statement added that the executions, which it documented based primarily on interviews with eyewitnesses and officials, "may be evidence of war crimes or crimes against humanity".
The current conflict in Iraq has acquired strong sectarian overtones. The Shia-led government is struggling against predominantly Sunni Isis fighters, and other Sunni rebel groups.
Meanwhile, reports say the Iraqi Kurds have taken over the northern Bai Hassan and Kirkuk oilfields, amid a growing dispute with the government in Baghdad.
The Iraqi oil ministry has condemned the seizure, saying it expects Kurdish fighters to "support security forces in confronting terrorist groups rather than using the conditions to raid and occupy oil fields".
Kurdish MPs have also withdrawn from Iraq's central government, after Prime Minister Maliki accused the Kurds of harbouring extremists.
On Saturday, the United Nations' special envoy to Iraq, Nickolay Mladenov, warned that the country could plunge into chaos if its parliament failed to agree on the formation of a new government.
The failure to choose the three critical government posts of prime minister, president and speaker would "only serve the interests of those who seek to divide the people of Iraq", he said in a statement.
More than a million people have fled their homes as a result of the fighting in recent months.