The Australian Defence Force (ADF) says its fighter jets may have caused the deaths of up to 18 civilians in a strike on Islamic State (IS) militants in Iraq.

The incident in 2017 was part of the US-led coalition’s bid to retake Mosul. However, the ADF said it was impossible to « definitively know » whether its forces, another coalition strike or « other actors » killed the civilians.

The deaths were « highly regrettable », military officials said.

Air Marshal Mel Hupfeld said two Australian F/A-18F Super Hornets had bombed IS militants in a residential area on 13 June 2017, following a request by Iraqi ground forces. A separate strike by unidentified coalition force took place simultaneously in the same street.

Despite post-strike surveys failing to detect civilian deaths, « credible » reports of casualties later emerged, Air Marshal Hupfeld said.The allegations were first raised publicly by Airwars – a group monitoring civilian deaths – which suggested up to 34 people had died.

Following an investigation launched in January last year, the ADF determined that between six and 18 civilians were unintentionally killed – a figure based on population density estimates. « Our pilots and decision-makers involved in the targeting process do everything they can to avoid civilian casualties, but sometimes it is not possible, » he said.

Air Marshal Hupfeld said the Australian strikes had accurately hit their targets and been carried out according to protocol. As a result, no penalties or other actions would be taken.

At least 1,190 civilians have been « unintentionally killed » as a result of coalition air strikes in Iraq and Syria since 2014, the joint force said in a statement on Thursday. It is still working its way through a list of other allegations.

Air Marshal Hupfeld said any compensation actions would be handled by the joint force’s central command.