Fighters of the Islamic State stand guard at a checkpoint in the Northern Iraq City of Mosul
Fighters of the Islamic State of Iraq and the Levant (ISIL) stand guard at a checkpoint in the northern Iraq city of Mosul, June 11, 2014. Picture taken June 11, 2014. REUTERS/Robert Stringer

The grandfather of the Australian boy who held a soldier's decapitated head while posing for the camera was sickened by what he saw. The young boy was reportedly forced to hold the head of an executed soldier in Syria.

The photo showing the Australian jihadist's son went viral. Many political and religious leaders condemned the gruesome image. According to reports, new details have emerged about how the Australian convicted terrorist Khaled Sharrouf had managed to bring his family out of the country. He allegedly arranged for his children to fly to Malaysia and booked return tickets to mislead authorities.

Sharrouf's father -in-law, Peter Nettleton, told The Australian that he was "devastated" to see the photo of his grandson holding a decapitated head of a dead soldier in the town of Raqq in northern Syria. The image was originally seen in a Twitter account believed to be owned by Sharrouf.

Reports said the boy may be not older than 10. He used two hands to hold the bruised and severed head. Nettleton said he felt sorry for his daughter and Sharrouf's wife, Tara.

Australian Prime Minister Tony Abbott condemned the image and said it only showed some of the "atrocities" Islamic militants were capable of. The jihadist group ISIS has overrun many areas of Syria and Iraq after mass killings including Christians and Yazidis.

Former army chief Peter Leahy remarked that the sickening image only reinforced his belief that the fight against Islamic terrorism may last 100 years. He said the "vast majority of Muslims" would be shocked to see the image. Leahy added that Islamic leaders should come forward and express their objection against this kind of behaviour publicly.

While most Islamic leaders refused to condemn ISIS, they agreed in condemning Sharrouf and the way he treats his sons.

Sheik Gul Saeed Shah, president of Board of Imams Victoria, warned young Muslim men not to travel abroad to join the jihad. He advised them to practise the religion since it is their right and don't get themselves killed.

Iraqi ambassador to Australia Mouayed Saleh remarked that children who are exposed to violence will "become wild animals" when they grow up.

A spokesman for the Attorney-General's Department said that in the event the children of Sharrouf will return to Australia, the government can coordinate with child protection services to discuss their future.