The persecution of entire communities and systematic violations, documented by UN human rights investigators, would amount to crimes against humanity and war crimes under international law, she said in a statement.

“Grave, horrific human rights violations are being committed daily by [ISIL] and associated armed groups,” Pillay said, citing targeted killings, forced conversions, abductions, slavery, sex crimes, forced recruitment and destruction of places of worship.

“They are systematically targeting men, women and children based on their ethnic, religious or sectarian affiliation and are ruthlessly carrying out widespread ethnic and religious cleansing in the areas under their control.”

Christians, Izadis and Turkmen were among the minorities targeted by the Takfiri group, she said.

After the Al-Qaeda splinter group seized control of Mosul on June 10, it loaded up to 1,500 prisoners from the city’s Badush prison onto trucks and took them to a vacant area for screening, Pillay said. Sunni inmates were taken away again on the trucks.

“[ISIL] gunmen then yelled insults at the remaining prisoners, lined them up in four rows, ordered them to kneel and opened fire,” she said, adding that up to 670 inmates lost their lives.

“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,” said Pillay, who steps down on Aug. 31 after serving six years as UN rights boss.

In Nineveh province, hundreds of Izadis were killed and up to 2,500 kidnapped in early August, Pillay said, citing testimony from victims and witnesses.

Those who agreed to convert are being held by ISIL but witnesses report that among those who refused, “men were executed while the women and their children were taken as slaves and either handed over to [ISIL] fighters as slaves or threatened with being sold,” the UN said.

Pillay called on the Iraqi government and international community to protect vulnerable ethnic and religious groups.

These included at least 13,000 Shia Turkmen in Salahuddin province besieged by ISIL forces since mid-June amid “fear of a possible, imminent massacre” and Izadis in besieged villages of Sinjar who remain at “serious risk,” she said.

BA/BA