Iraqi government forces have tortured and killed villagers south of Mosul, Amnesty says in the first such report of alleged rights abuse in the US-backed campaign to retake the city from Islamic State.
The New York-based rights group said victims included "up to six" people found last month in the Shura and Qayyara sub-districts who security forces suspected of ties to the ultra-hardline jihadist group which seized a third of Iraqi territory in 2014.
"Men in Federal Police uniform have carried out multiple unlawful killings, apprehending and then deliberately killing in cold blood residents in villages south of Mosul," said Lynn Maalouf, deputy director for research at Amnesty's Beirut office.
Spokesmen for the federal police and the Interior Ministry, to which they belong, could not be reached for comment.
The Mosul operation, involving a 100,000-strong alliance of troops, security forces, Kurdish peshmerga and Shi'ite Muslim militias and backed by US-led air strikes, has entered its fourth week but has so far gained just a small foothold in the city.
Amnesty's report described several incidents on or around October 21 in which separate groups of men were beaten with cables and rifle butts before being shot to death. In one case, a man's head had been severed from his body, it said.
Amnesty said that without accountability, the alleged abuses risked being repeated in other towns and villages as the Mosul offensive continues.