The terrorist group once known as the Islamic State of Iraq and Syria (ISIS) is now seen as the most dangerous extremist group in the world.

Who is the Islamic State (IS)?

THIS is a photo that will shock the world.

Sydney jihadist Khaled Sharrouf’s son — a child, 7, raised in the suburbs of Sydney — struggles with both arms to hold up the decapitated head of a slain Syrian soldier.

According to a report in The Australian newspaper, the horrifying image was posted on Twitter by a proud father with the words “That’s my boy” and is set to reverberate around the world as a savage example of the brutality of the Islamic State.

Full story: Sharrouf kids witness war’s horror in Islamic State

Sharrouf, a convicted terrorist who fled to Syria last year and is now an Islamic fighter, is believed to be travelling with his family.

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According to the report, Sharrouf’s son is pictured holding the severed head while wearing a pair of checked pants and a blue shirt with the insignia Polo Golf Kids.

In the photographs featuring Sharrouf and his son the heads are blackened and bloated having been dead for a week.

Prime Minister Tony Abbott said the image was evidence of the “hideous atrocities” such groups are capable of.

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

Former army chief Peter Leahy told 3AW the image was beyond belief and he called on the Islamic community leaders to address the matter urgently.

“This sort of ideology that can support a father doing this and can support this sort of activity that we’re seeing across the Middle East...let’s hear the leaders in the Islamic community condemn this type of activity because if they don’t what are they thinking,” he said.

Also speaking to 3AW, Monash University Global Terrorism Research Centre director Greg Barton said the children would probably follow in their father’s footsteps.

“Having Australian children there I think will horrify the nation but I think it reinforces the concerns that we’ve been taking over the past few weeks and authorities have been warning us about the threats back home here in Australia,” he said.

Sharrouf, a convicted terrorist, is wanted by the AFP over his crimes in Syria and Iraq. In another image he is posing in his battle-fatigues with his three children, aged four, six and seven and all armed with machineguns.

The horrific images come after revelations that kids are being coached to kill in the name of religion as Islamic State prepares a generation of fighters to rid the world of “infidels”.

Chilling footage from inside the newly founded “state” shows children as young as nine being prepared to pick up arms to continue the brutal onslaught against infidels worldwide.

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Young Abdullah is one of the so-called generation of the caliphate, an ancient term used to describe a new Islamic state built on bloodshed in northern Iraq and Syria.

As tens of thousands of Christians and minority group members flee certain death at the hands of the militants, an alarming new documentary by US media group Vice News reveals a new generation are being trained by Islamist terrorists in sharia camps to destroy infidels, including America and her allies.

Encouraged by his father, young Abdullah tells filmmaker Medyan Dairieh how he plans to kill the infidels.

“What do you want to be, a jihadist or to execute a martyrdom (suicide) operation?” Abdullah’s father, Abdullah Al-Belgian, an Islamic State (IS) leader who operates a preaching van, asks.

“A jihadist,” Abdullah replies.

Father: “Why do we kill the infidels? What have the infidels done?”

Abdullah: “They kill Muslims.”

His father tells Dairieh he left his home in Belgium to join fighters from the formerly al-Qaeda-linked IS terrorist group, originally named ISIS (Islamic State of Iraq and Syria), which has captured territory in Iraq and Syria.

Asked whether people had responded to his message, he replies: “Yes, many, many, many people are responding, especially the young men.”

Another IS member explains: “For us we believe that this generation of children is the generation of the caliphate.

“God willing, this generation will fight infidels and apostates, the Americans and their allies,” he continues.

“The right doctrine has been implanted in these children. All of them love to fight for the sake of building the Islamic State and for the sake of God.”

Those aged 15 years and under are sent to sharia camp to be taught about “their creed and religion”.