Chief of Joint Operations David Johnston confirmed Australia’s involvement in that civilian casualty on June 7 as well as a separate incident on March 30, also in west Mosul.
Amnesty International Australia criticised the timing of the announcement – which has coincided with Saturday’s AFL grand final.
In July, the rights group released a damning report on civilian casualties in west Mosul, urging the US-led coalition to take more care to protect the lives of innocent people.
“It’s extremely disappointing it has taken the Australian government until now to release information about Australia’s involvement in civilian casualties, including the possible killing of a child” spokeswoman Diana Sayed told AAP.
In the June incident, Iraqi Security Forces were in a gun battle with Islamic State militants about 20 metres away and found themselves “pinned down”, Vice Admiral Johnston said.
A pair of Australian Super Hornets were nearby and were called in to provide air back up, following normal targeting procedures.
“It was a residential building, but it was assessed a legitimate target,” he said.
A single weapon – a GPS guided bomb – was dropped on the front of the building and it’s believed two IS fighters were killed.
Vice Admiral Johnston said no civilians had been observed in the area before the strike however afterward it became apparent some had been inside, as they “calmly” exited the rear of the building that was hit.
“A civilian was either seriously injured or killed as a result of that strike,” Vice Admiral Johnston said.
“It was a child carried out.”
The Australian fighter pilots reported the incident to the US-led coalition’s headquarters and up the Australian chain of command for investigation.
Vice Admiral Johnston insisted Australian rules of engagement had been followed and the strike complied with the laws of armed conflict.
The strike had successfully protected Iraqi soldiers on the ground, he said.
Meanwhile, in the March incident, a group suspected of being IS fighters had been positioned about 300 metres away from Iraqi Security Forces.
The US-led coalition authorised an air strike and seven civilians were killed or injured, including a child.
Australian aircraft were not involved in that strike but Australian defence personnel had been involved in the target decision-making process.
“It appeared the group was wrongly identified (as IS),” he said, adding that at the time the information the group was armed had come from a credible and reliable source.
The US-led coalition estimates, there have been 735 civilian fatalities since 2014 and 350 incidents are still under investigation.
Airwars, a non-government group monitoring air strikes and civilian deaths in the Middle East estimates close to 5500 civillians have died in coalition air strikes in Iraq and Syria.
0:00 Australian soldiers teaching Afghans how to fight Share Australian soldiers teaching Afghans how to fight