The U.S.-led air campaign against the Islamic State group in Iraq and Syria has killed nearly 460 civilians over the past year, including more than 100 children, according to a report by Airwars -- a project led by a team of journalists and researchers.

The U.S. and its allies have conducted more than 5,000 airstrikes across northern Syria and Iraq in their attempt to push back the Sunni militant group. Although several groups have documented the deaths of civilians in the region, the U.S. military has, so far, acknowledged only one incident involving the deaths of civilians -- an airstrike in Syria’s Idlib province in November that led to the “unintentional” death of two children.

“Despite claims by the US-led Coalition that its airstrikes in Iraq and Syria are ‘the most precise and disciplined in the history of aerial warfare’, there are clear indications from the field that many hundreds of non-combatants have been killed by the 12 international allies in the first year of their air war against Islamic State,” the U.S.-based organization said, in a report released Monday.

syria iraq death Coalition airstrike locations in Syria and Iraq. Photo: Airwars/B. Simon

According to earlier reports by the Syrian Observatory for Human Rights -- which relies on a network of local activists -- at least 173 civilians, including over 50 children, have so far died in airstrikes carried out by the U.S. and its allies in Syria. Airwars, in its report, put the figure much higher, estimating that up to 354 non-combatants may have been killed.

“In total … some 118 incidents of concern had been flagged across Iraq and Syria by international and local news organisations, by monitoring groups and by social media sites,” Airwars said, in its report. “Some of these events are poorly reported. Others are contested -- or did not involve the deaths of civilians as initially claimed. Even so, Airwars has identified 52 incidents of significant concern across both Iraq and Syria in which the level of public reporting appears reasonable, and where Coalition airstrikes are confirmed in the near vicinity for that date.”

One of the worst civilian casualty incidents claimed by the report took place in Iraq in June 2015. Up to 70 civilians, including 26 children, are believed to have died when coalition aircraft bombed an ISIS explosives factory in the town of Hawijah, in northern Kirkuk province.

“The coalition confirms that it carried out the strike at Hawijah, though a senior commander later insisted that only a ‘fairly small weapon’ had been used in the attack -- and that any responsibility for civilian deaths ‘rests squarely on Daesh [ISIS],’” Airwars said, in the report.

The latest report documenting civilian deaths came even as the British government announced that it would extend its air campaign against ISIS in Iraq by one year to March 2017. The move, the British defense secretary reportedly said, is necessary to help Iraqi Kurds reclaim lost territory from the militant group.