Iraq crisis: Australian national fighting for Isis in Syria tweets photograph of son holding up severed head and writes ‘that’s my boy’

An Australian man fighting for the Isis militant group has reportedly posted a picture online showing his young son holding the severed head of a Syrian soldier, with the caption: “That’s my boy.”

The image has been condemned by the Australian Prime Minister, Tony Abbott, who said it provides further evidence of “just how barbaric” the Islamist organisation is.

It comes after the Iraqi government said “striking evidence” had been obtained that Isis had murdered at least 500 of the Yazidi ethnic minority, including burying women and children alive.

According to The Australian, the photograph is of convicted terrorist Khaled Sharrouf’s son, who has not been named but was raised in Sydney and appears to be under the age of 10.

The newspaper said it was posted on Twitter by the boy’s proud father, and that Sharrouf posted beneath the image that it was taken in the northern Syrian city of Raqqa – the “capital” of Isis’s self-declared new Islamic Caliphate.

Mr Abbott, who is currently in the Netherlands, said Australia would be joining Britain, the US and other countries in humanitarian efforts to help the tens of thousands of Yazidi people trapped on the Sinjar mountain range.

He said that the persecution of the archaic but colourful religious minority was “a potential humanitarian catastrophe”, and that Isis’s quest for an Islamist nation more generally posed “extraordinary problems” for the region and the wider world.

“We see more and more evidence of just how barbaric this particular entity is,” Mr Abbott said.

Sharrouf was among nine Muslim men accused in 2007 of stockpiling bomb-making materials and plotting terrorist attacks in Sydney and Melbourne, Australia’s two largest cities.

He pleaded guilty to terrorism offences and was sentenced in 2009 to four years in prison, as well as being banned from leaving the country – but last year used his brother’s passport to leave Australia with his wife and three sons to fight in Syria and Iraq.

Australian police announced last month that they had issued arrest warrants for Sharrouf and his companion Mohamed Elomar, another former Sydney resident, for “terrorism-related activity”.

Elomar reportedly appeared in a photo on Sharrouf’s Twitter account holding the severed heads of two Syrian soldiers, while in June The Australian published a picture of himself posing among the bodies of massacred Iraqis. They will both be arrested if they return to Australia.