Members of Iraqi government-allied Sunni tribal militias have brutally tortured men and boys suspected of having ties to the Islamic State (ISIS/ISIL) in villages outside the city of Mosul, in some instances using tasers, locking them in cages, and strapping them to vehicle bonnets and parading them through the streets, reports the human rights watchdog group Amnesty International.

“Some residents told Amnesty International that they believe that the tribal militia were motivated by revenge for relatives killed by [ISIS], as well as longstanding enmities unrelated to the conflict,” notes the group.

The watchdog group has identified the Sunni tribesmen — who reportedly carried out the atrocities in recent days while participating in the ongoing U.S.-backed Iraqi offensive to liberate Mosul from the Islamic State — as fighters from the Sab’awi Tribal Mobilization militia (Hashd al-‘Ashairi) and the Firsan Jbour tribal militias.

“There is strong evidence that Sab’awi tribal militia members have committed crimes under international law by torturing and otherwise ill-treating residents in [the villages of] Qati’ al Sab’awi in in revenge for crimes committed by IS,” declared Lynn Maalouf, deputy director for research at Amnesty International’s Beirut branch.

“There is no doubt that IS fighters who are suspected of committing crimes must be held accountable in fair trials, but rounding up villagers and forcing them to endure public humiliation or other violations, including torture, is no way of securing justice, truth and reparation for victims of IS crimes,” she added.

Citing eyewitness accounts, the human rights groups reveals that members of the Sab’awi militia have arrested men and boys from villages in southeastern Mosul without a warrant.

One witness told Amnesty International that six Sunni tribesmen dragged a man identified only as “Ahmed”  into the courtyard of his house and accused his brother of being an ISIS member “before brutally beating him in front of his wife and children.”

“They kicked him to the ground and ‘tasered’ him three times. They punched him and beat him with the back of their Kalashnikovs, with metal rods, and even a rubber hose — the thick ones used for agriculture,” declared the witness, adding that the victim was unable to stand after the beating.

“Every fighter from the Hashd had his own personal revenge to take… They drove around the village with men strapped onto car bonnets shouting things like ‘come see the [ISIS member] who informed on me and my father,’” added two witnesses.

Sab’awi tribesmen have carried out the arbitrary arrests around the clock despite the arrival of a large convoy of Iraqi military troops on October 22, notes Amnesty International.

“A group of detainees was handed over to the Iraqi armed forces on 30 October, bearing marks of torture, according to witnesses,” adds the human rights watchdog. “Others are believed to still be held by the Tribal Mobilization fighters in unofficial detention facilities, including abandoned homes in villages [on the outskirts of Mosul].”

Amnesty International also learned from witnesses that members of the Sunni Firsan Jbour tribal militias were abusing civilians outside of Mosul.

“Witnesses told Amnesty International that on 26 October, militia fighters at checkpoints taunted them for belonging to [ISIS], spat and threw rocks at them and threatened to kill or detain those with IS links as they were being transported to safer areas by Iraqi forces,” it reports.

Sunni tribesmen are participating in the U.S.-backed Mosul offensive as part of a force that also includes tens of thousands of Iraqi Security Forces, Kurdish Peshmerga troops, Christian fighters, and Shiite militiamen, many backed by Iran. Sunni-majority Mosul, Iraq’s second-largest city, is the terrorist group’s last urban stronghold in the country.

Amnesty International reports:

All the witnesses interviewed described a disturbing scene in which seven men and boys, between the ages of 16 and 25, were placed in large poultry cages on display in the middle of a public roundabout. A Tribal Mobilization fighter asked each to walk out of the cage in turn saying to them: ‘What are you? Say you’re an animal, say you’re a donkey,’ before beating them and forcing them into cars.

American Maj. Gen. Gary J. Volesky, commander of the U.S.-led coalition’s land component and commander of the storied 101st Airborne Division, has acknowledged that the United States is backing some of the Sunni tribesmen fighting in the Mosul operation.

“Iraqi authorities have repeatedly failed to stop revenge attacks or investigate crimes by militias from the [Iran-backed predominantly Shiite] Popular Mobilization Units [PMU], who are also participating in the Mosul offensive. This has fostered a dangerous culture of impunity in which perpetrators of such attacks feel they have free rein to commit crimes and go unpunished,” noted Maalouf.

“The authorities must rein in the tribal militia fighters responsible and bring them to justice, in order to prevent such crimes being repeated in the ongoing Mosul offensive. Those suspected of committing crimes must be removed from duty without delay,” she added.