A Yazidi militia killed 21 civilians and abducted 40 more in revenge attacks on Sunni Arab villages in the Sinjar region of Iraqi Kurdistan, Amnesty International said Wednesday. Seventeen people remain missing and are feared dead, according to their families.

The alleged massacre took place on January 25 this year in the villages of Sibaya and Jiri. In Jiri, the Yazidi militia killed 11 people — 10 men, and a 15-year-old boy — and injured many more, including children. Then in nearby Sibaya, those who had not or could not flee, including elderly and disabled people, were shot at close range, execution style, according to the report.

"Most were shot point-blank in and around their homes and three were taken by the assailants and were later found dead in nearby Yezidi villages," the report said. "By the time the attackers reached Sibaya in the afternoon, most of the residents had fled, having heard of the killings in Jiri. The militias however did not spare those who stayed behind: they killed eight men and women who were elderly or had physical disabilities and two children."

Kurdish security forces dispute Amnesty's account, and say they were fired at and a firefight ensued, during which "some Arabs were killed." They said they led many women and children to safety and say the 17 missing men have joined ISIS.

After initial reports of the massacre surfaced, Amnesty International's Senior Crisis Response Advisor Donatella Rovera visited the area in April, and spoke to 30 people who she said gave consistent testimonies that there was no gunfight firefight, but rather that the militia singled out men and executed them.

"Two armed Yazidis in uniforms stormed into our home and told us to get out," Jiri resident Nahla Meri told Amnesty. "We did as they told us and as we got outside they shot my husband and my son Salah. They killed them both. They shot several times, at him and near him. One of the bullets went through the blanket in which I had wrapped my baby, who I was holding in my arms. Luckily the bullet did not harm the baby."

Residents who managed to flee Sabiya after the news of the massacre in Jiri described how fear of further attacks kept them from collecting their dead for one, or several, days.

"We had to sneak into the village like thieves, to find our relatives killed and our homes destroyed, because if the Yazidis see us from the hills they may come to attack us again," one resident told Amnesty International.

An interview) with a Yazidi miltia commander from the time quotes the Yazidi commander complaining that Kurdish forces — the PKK and YPG — attacked the village, abducted Sunni women and killed a young Yazidi. This contrasts sharply to the version given by a woman who said she was among the captives:

"They wanted to take us women and children to Mount Sinjar (the headquarters of the Yazidi militias) but luckily the Peshmerga came and saved us," the woman told Amnesty.

Rovera said during her research that senior leaders from the Yazidi militias summoned her as soon as she arrived in Sinjar after it became known she was speaking to villagers about the alleged events.

"They were incredibly nervous," Rovera said. "They don't like this being talked about. They were very aware of what happened, and the response was not very constructive because their version of events was so far out from reality, that it did not make any sense."

The report's allegations confirm fears that the Islamic State's domination of parts of Iraq would cause non-Sunni Iraqis to target the country's Sunni community for their perceived co-operation with the militant fighters. Kurdish authorities, Rovera says, must act to stop these kinds of attacks in order to enable Sunnis return to their homes.

"Iraq has descended into absolute chaos of revenge and retaliation, and reprisals and attacks and counterattacks have really escalated," Rovera said. "They have not targeted the militants, they have done tremendous damage to the fabric of society, and to ordinary people, who cannot defend themselves."

Rovera says the Kurdish authorities appear be mirroring the response of the Iraqi central government to the Islamic State's gains in Iraq: To keep Sunnis out of their homes within the territory they have managed to take back from IS.

"These villages were a pretty easy target because they are very close to the places where there is now the Yazidi militias and they are very small populations," Rovera said. "As of now, the Kurdish authorities have generally prevented Arabs from going back to their villages. "

Tikrit, she said, is a similar case. Despite being liberated more than six weeks ago, "not a single Sunni Arab has went back", and there are many places that have been liberated months ago from IS where Sunnis have been prevented from returning.

"I don't expect Arabs to be allowed back into areas that were under the control of the Kurdish regional government, and even less so in the Sinjar areas," Rovera said. "That is how the Kurdish authorities have dealt with it, but this is clearly not satisfactory. You can't just say the Sunnis are not allowed back to their homes and villages. Where are they going to go?"

Follow Lara Whyte on Twitter:@larawhyte

Watch the** VICE News documentary, "T**he Battle for Iraq: Shia Militias vs. the Islamic State."