Between 9,000 and 11,000 people were killed in the nine-month battle to recapture the Iraqi city of Mosul from the daesh group (ISIL), an Associated Press (AP) investigation has found.
The civilian casualty rate is nearly 10 times higher than that previously reported.
The deaths are acknowledged neither by the coalition, the Iraqi government nor the daesh's self-styled caliphate.
Iraqi or coalition forces are responsible for at least 3,200 civilian deaths from air raids, artillery fire or mortar rounds between October 2016 and the fall of ISIL in July 2017, according to the AP investigation.
The news agency cross-referenced morgue lists and multiple databases from non-governmental organisations.
Most of those victims are simply described as "crushed" in health ministry reports.
The coalition, which did not send anyone into Mosul to investigate, acknowledges responsibility for only 326 of the deaths.
"It was the biggest assault on a city in a couple of generations, all told. And thousands died," said Chris Woods, head of Airwars, an independent organisation that documents air and artillery attacks in Iraq and Syria and shared its database with AP.
"Understanding how those civilians died, and obviously ISIS played a big part in that as well, could help save a lot of lives the next time something like this has to happen. And the disinterest in any sort of investigation is very disheartening," Woods said.
In addition to the Airwars database, AP analysed information from Amnesty International, Iraq Body Count and a United Nations report.
AP also obtained a list of 9,606 names of people killed during the operation from Mosul's morgue.
Hundreds of dead civilians are believed to still be buried in the rubble.
Of the nearly 10,000 deaths that AP found, around a third of the casualties died in bombardments by the US-led coalition or Iraqi forces.
Another third were killed in ISIL fighters' final frenzy of violence. It could not be determined which side was responsible for the deaths of the remainder.
But the morgue total would be many times higher than official tolls.