BEIRUT, Lebanon — More than 450 civilians are thought to have been killed in the US-led bombing campaign against the Islamic State (IS) since it began a little under a year ago, according to a new report.

Using a wide range of sources, including local media, witness reports, social media and video evidence, Airwars concluded that the campaign in Iraq and Syria, which began on Aug. 8 last year, is responsible for between 459-591 civilian fatalities.

Airwars is an independent investigative project that monitors reports of civilian casualties caused by the coalition in the fight against IS.

Its figures stand in stark contrast to the two civilian casualties acknowledged by the anti-IS coalition as “likely” being caused by its airstrikes.

​The discrepancy indicates “a worrying lack of urgency on the part of all coalition members regarding civilian deaths,” the report said.

One of the problems is that the coalition’s own monitoring systems appear woefully inept at identifying and investigating incidents where civilian casualties have been reported. Airwars estimates that coalition officials “appear to have identified only one-third of 118 alleged cases of concern” as of June 2015.

Lt. Gen. William C. Mayville Jr., joint staff director of operations, speaks about airstrikes in Syria during a briefing at the Pentagon in September 2014 in Washington, DC.

The reports of civilian casualties are nothing new. Back in April it was apparent that hundreds of civilians may have been killed by the coalition.

A GlobalPost investigation into the manner in which airstrikes were carried out revealed a process that raised questions about the rosy descriptions of the bombing campaign by coalition officials, such as its lead commander, Lt. Gen. John Hesterman, who called it “the most precise and disciplined in the history of aerial warfare.”

In one incident recounted by a Kurdish peshmerga commander in Kirkuk, Iraq, coalition jets bombed a group of alleged IS fighters 25 minutes after receiving intelligence through a second-hand source.

The peshmerga commander described a two-step process for calling in an airstrike. He receives intelligence on a particular target — or is given it by a trusted source — then the coalition verifies that information from the air. If the intelligence lines up, the jets launch their missiles (American jets carry out roughly 85 percent of all coalition airstrikes against the Islamic State).

In response to questions from GlobalPost about safeguarding civilians, US Army Capt. John J. Moore, a spokesman for the coalition, said in April that there is "a detailed, multi-echelon process between the coalition partners, as well as the Iraqi Ministry of Defense. Without their request and approval, a strike will not occur."

The high civilian toll not only inflicts further pain and suffering on a beleaguered and in some cases besieged population, it threatens to undermine the very aim of the campaign: to “degrade and destroy” the Islamic State.

As the report notes: “The present Coalition policy of downplaying or denying all claims of non-combatant fatalities makes little sense, and risks handing Islamic State and other forces a powerful propaganda tool.”

From the report: airstrike case studies

June 3rd 2015: Hawijah, Kirkuk province, Iraq In the worst alleged civilian casualty incident for Iraq to date, up to 70 non-combatants and many more militants were reportedly killed when Coalition aircraft struck an Islamic State IED factory in the town of Hawijah in early June. The secondary explosions which followed devastated the surrounding neighbourhood. Eyewitness Hassan Mahmoud al-Jubbouri later told Reuters the area looked as if it had been hit by a nuclear bomb, and described personally pulling the bodies of a family of six from the rubble. Casualty counts varied significantly, with few details of individual victims so far emerging. Only one victim has been publicly named — Kherallah Ahmed Al Saleh Al Thawabi, described as the owner of a car maintenance shop in the area. The head of Kirkuk’s Arab Council, Mohammed Khalil al-Jubouri, placed the total number of dead and injured civilians at 150. The Iraqi Revolution website claimed 70 civilians had died, with more than 100 injured. And news agency Rudaw also reported 70 killed, describing 26 children and 22 women among the dead. 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.’ However on June 24th the Pentagon announced a formal inquiry into what it now views as ‘credible’ claims of civilian deaths.