While refusing to comment directly on the case of Sharrouf and his two sons, reported killed in an airstrike in Syria last week, Major General Rupert Jones said the global coalition goes through "really detailed, targeted processes."

Speaking to international journalists in London from Baghdad via Skype, General Jones said: "This is the most precise, targeting process that I think any coalition has ever achieved in any previous conflict," he said.

He declined to give any details about Sharrouf's death but said in general children on the battlefield would be treated differently but it would not always be possible to tell if they comprised part of a target or not.

"If you can patently see they're children then you're going to treat them as children but that will often be quite difficult to define, you can't necessarily tell the age of an individual," he said.

"We go to the very, very greatest lengths possible to make sure that casualties are minimised."

He said the military always aims for zero civilian deaths but said that the licence to kill is greater depending on the target.

"If you're going after [Islamic State leader Abu Bakr] al-Baghdadi would we take a bit more risk than if we were going after some low-level fighter? Yes and I think nations would expect us to do that," he said.

Sharrouf slipped out of Australia using his brother's passport to join Islamic State in 2013. His wife, Tara Nettleton joined him soon after with their five children Zaynab, 15, Hoda, 14, Abdullah, 12, Zarqawi, 9, and Humzeh, 6. In an image that made international headlines, Abdullah was photographed holding a severed head of a Syrian soldier in 2014.

Abdulla and Zarqawi are believed to have been killed in the strike on August 11. Zaynab was married to another Australian foreign fighter Mohammed Elomar and gave birth to a child. Elomar is thought to have been killed in an air strike in Syria in 2015, the same year the mother of the Sharrouf children, Tara Nettleton died from appendix surgery in Syria.

The global coalition issues a monthly report on the number of civilians killed. It disputes claims by Airwars of nearly 5,000 innocent casualties and says the figure of verified civilian deaths is 624. To date, based on data between August 2014 and June 2017, the Coalition conducted a total of 22,983 strikes that included 48,636 separate engagements.

"Now I'm not saying to you that is the totality but that is the totality that has been presented to us, of credible cases that we've been able to investigate and resolve," he said.

But he said it was impossible to liberate cities like Mosul and Raqqa without civilians being caught in the crossfire. "You can't defeat Daesh without there being some price, our job is to keep that price as small as possible."

'Surrender or die'

General Jones said there were "undoubtedly" foreign fighters in the last remaining strongholds of Raqqa in Syria and Tal Afar and the remainder of Ninewah province in Northern Iraq.

He said it was becoming extremely difficult for them to escape via Turkey and infiltrate Europe or countries in the north of Africa, saying there was no evidence of many fighters leaving cities like Mosul and Raqqa.

"It's equally hard to move back out, in the same way if you can't get across through Turkey easily, you can't get out easily either," he said.

He quoted Iraq's Prime Minister Haider al-Abadi saying ISIS fighters had one of two options: "surrender or die."

Australia is hoping that within months, Islamic State recruiter Neil Prakash will be returned home to Australia to face terrorism charges. He was caught trying to escape Syria via Turkey last year.

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