The US-led coalition killed as many as 9,600 civilians in the battle against Isil, a death toll from Western military action “not seen since the Vietnam war”, a monitoring group has found.

The coalition is responsible for more than a third of the estimated 25,000 civilian deaths in Syria and Iraq since launching its offensive against the jihadists in 2014, according to a new report by UK-based Airwars.

Airwars found that its heavy use of explosive weapons unintentionally inflicted large numbers of casualties, despite the “precise” nature of many of those bombs.

The figure is 10 times higher than the one given by the coalition, leading experts to describe it as the least transparent military campaign in US history.

When discussing the battles against the Islamic State of Iraq and the Levant (Isil), the coalition described a target-selection process grounded in meticulously gathered intelligence.

But Airwars claims in its report that the size of ammunition used may have undermined key benefits of so-called smart bomb technologies. Deployed in densely-populated areas, they caused devastating effect.

In the most widely covered civilian casualty incident in the Iraqi city of Mosul a March 17, 2017, coalition air strike on homes in the Jadidia neighbourhood saw at least 105 civilians killed.