IS fighter's 8yo son asked 'how to kill an Australian'

The eight-year-old son of an Australian-born Islamic State fighter has been pictured in a video holding firearms and a knife and making threats in the name of the terrorist group.

The recent video, which is being investigated by Australian authorities, also shows Khaled Sharrouf's son Humzeh being asked "how do you kill an Australian?", The Daily Telegraph reports.

The boy, the youngest of Sharrouf's five children, wears a suicide vest and answers the question his father poses while off camera and also makes a number of statements supporting IS.

It's being described by Australian Cabinet Minister Matthew Canavan as "child abuse".

"I don't think you could think of a greater form of child abuse to be subjecting a kid to that kind of propaganda, to almost turn them into a murderer so to speak," he told Sky News.

'It is reprehensible. It has to be condemned, and I trust that the proper authorities will look into this matter."

Senator Canavan said he had sympathy for the child.

"It's not his fault that his father is an evil megalomaniac seeking to abuse his own children, but I don't know enough about the individual circumstance."

NSW Police say multiple agencies are investigating the video, but say there is no "specific threat" to Australia, which is currently has a terror level of 'probable'.

Sharrouf went to Syria to fight for Islamist State in 2013, a year after he was released from jail having been sentenced for his part in a terror plot.

He made headlines in 2014 when photos surfaced of another of his young sons holding the severed head of a Syrian soldier.