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 said in a statement.

The prisoners were all Sunni Muslims, while the majority of security forces and militia were Shia, they added.

Meanwhile, Iraqi Kurds have reportedly taken over two oilfields in the north.

Most of the executions took place as Iraqi forces fled advancing Isis fighters, HRW said in a statement.

The killings took place in six Iraqi villages: Mosul, Tal Afar, Baquba, Jumarkhe, Rawa and Hilla, HRW reported.

"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".

(BBC)