WASHINGTON: A US military investigation acknowledged on Thursday that more than 100 civilians were killed in a US air strike on a building in the Iraqi city of Mosul in March during operations against the militant Islamic State group.

The probe concluded that the US strike in the Al Jadida district inadvertently triggered explosives placed in the building by IS fighters, causing it to collapse.

Local officials and eyewitnesses have said as many as 240 people may have died in the strike.

It is believed to be one of the single largest incidents of civilian casualties since the US-led coalition started operations against Islamic State in Iraq and Syria.

Air Force Brigadier General Matthew Isler, who oversaw the investigation, told reporters that the March 17 strike was aimed at two IS snipers.

However, the 225-kilogram bomb triggered explosives inside the concrete building, collapsing it onto civilians.

Isler said the United States and nearby Iraqi forces did not know there were civilians in the building or that it had been rigged with explosives.

He added that 101 civilians inside the building were killed, four civilians were killed nearby, and 36 civilians were still not accounted for.

Before this investigation, the US-led coalition against IS said that at least 352 civilians had been killed in strikes it carried out in Iraq and Syria since 2014. That estimate is far lower than those provided by outside groups.-REUTERS