AKIPRESS.COM - The United Nations on Monday condemned "appalling, widespread" crimes by Islamic State forces in Iraq, including mass executions of prisoners that could amount to war crimes.

U.N. human rights chief Navi Pillay condemned "grave, horrific human rights violations" being committed by Islamic State, a Sunni Muslim group which has seized large areas of Iraq and Syria to the alarm of the Baghdad government and its allies in the West.

Up to 670 prisoners from Badush prison in the city of Mosul were killed by Islamic State on June 10, Pillay said in a statement quoting survivors and witnesses to the "massacre" as telling U.N. human rights investigators.

"Such cold-blooded, systematic and intentional killings of civilians, after singling them out for their religious affiliation, may amount to war crimes and crimes against humanity," Pillay said.

Islamic State (ISIL) loaded 1,000 to 1,500 prisoners from the jail on to trucks and took them for screening, Pillay said. Sunni inmates were then separated and removed.

"ISIL gunmen then yelled insults at the remaining prisoners, lined them up in four rows, ordered them to kneel and opened fire," she said.