Iraqi security forces and militias affiliated with the government appear to have unlawfully executed at least 255 prisoners in six Iraqi cities and villages since June 9, Human Rights Watch reported July 11. The report notes: "The vast majority of security forces and militias are Shia, while the murdered prisoners were Sunni." At least eight of those killed were boys under age 18. The mass extrajudicial killings, which appear to be revenge killings for atrocities by ISIS, may be evidence of war crimes or crimes against humanity, HRW said. "Gunning down prisoners is an outrageous violation of international law," said Joe Stork, deputy Middle East director at HRW. "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." HRW called for an international commission of inquiry to investigate violations of the laws of war by all sides in the Iraq conflict.

Human Rights Watch documented five massacres of prisoners between June 9 and 21—in Mosul and Tal Afar in northern Nineveh province, in Baaquba and Jumarkhe in eastern Diyala province, and in Rawa in western Anbar province. In each attack, statements by witnesses, security forces and government officials indicate that Iraqi soldiers, police or pro-government militias extrajudicially executed the prisoners, in nearly all cases by shooting them. In one case the killers also set dozens of prisoners on fire, and in two cases they threw grenades into cells.

Most of the prisoners appear to have not even been fighters, but prison inmates who were summarily killed by government and pro-government forces before they abandoned the cities as ISIS swept south. The killings may have been partially motivated by the ISIS practice of conscripting Sunni prisoners in seized territory, but were also liklely revenenge for ISIS massacres of captured government troops. Summary executions by ISIS forces have been condemned by the UN High Commissioner for Human Rights.