The US-led coalition against so-called Islamic State appears to be failing to take adequate precautions to prevent civilian deaths during the battle for Mosul, Amnesty International says.
The group found evidence pointing to an “alarming pattern” of air strikes in the Iraqi city that had destroyed houses “with entire families inside”.
Witnesses say hundreds of civilians had died in such attacks this month.
There was no immediate response from the coalition to Amnesty’s report.
However, it has previously insisted that it takes all reasonable precautions during the planning and execution of air strikes to reduce the risk of harm to civilians.
“There is no military force in the world that has proven more sensitive to civilian casualties,” US Secretary of Defense James Mattis said on Monday.
The same day a spokesman said the Pentagon placed the “highest priority” on investigating claims there had been dozens or even hundreds of civilian casualties after air strikes in western Mosul.
Iraqi pro-government forces launched an offensive to recapture the city – the last major IS urban stronghold in the country – five months ago.
The coalition has supported the assault by carrying out hundreds of air strikes and deploying military advisers and special forces personnel on the ground.
Although more than 280,000 civilians living in the city have fled their homes during the fighting, many more have followed the government’s advice to stay put until they are reached by troops.
In one of the deadliest incidents, at least 150 people were reported killed in a coalition air strike in the Jadida district of western Mosul on 17 March.
The coalition has launched an investigation into the incident, and the US military said an initial review of data indicated that an air strike was carried out in the vicinity on that day.
However, the Iraqi military said its experts had inspected the site and found no evidence of an air strike. Instead, they saw the remains of a “huge, detonated booby-trapped vehicle”.
Hind Amir Ahmad, a 23-year-old woman, lost 11 relatives, including her parents, grandparents and four young siblings, in a reported air strike on 13 December in eastern Mosul.
“We were sleeping when the house literally collapsed on us,” she told Amnesty, adding: “We ran to my uncle’s house nearby.”
“At about 14:00 that house too was bombed and collapsed on us,” she said.
“Almost everyone in the house was killed – 11 people. My cousin, two aunts and I were the only ones who survived.”
In another air strike on 6 January, 16 people were killed in three adjacent houses in the Mazaraa district of eastern Mosul, according to Amnesty.
Survivors and neighbours told the group’s researchers that, as far as they knew, no IS fighters had been present in or around the house.
“Did the government, the coalition think how to protect the civilians in this war? It doesn’t seem so,” said Ahmed, a relative of the victims.
Donatella Rovera, who carried out the field investigations in Mosul, said the level of civilian deaths “suggests” that coalition forces had “failed to take adequate precautions”.
“The fact that Iraqi authorities repeatedly advised civilians to remain at home… indicates that coalition forces should have known that these strikes were likely to result in significant numbers of civilian casualties.”
“Disproportionate attacks and indiscriminate attacks violate international humanitarian law and can constitute war crimes,” Ms Rovera said.