Islamic State militants and sympathisers are triumphantly circulating images of a 10-year-old boy they claim has been 'martyred' while fighting alongside his father in Syria.

Describing the child as ISIS' youngest jihadist, chilling photographs taken before his alleged death show him smiling at the camera, wearing military fatigues and brandishing a huge assault rifle.

ISIS sympathisers took to social media to identify the 'cub fighter' by his alleged nom de guerre Abu Ubaidah, adding that both he and his father were killed during clashes in Syria in recent weeks, but not specifying exactly where they died or who they had been fighting against.

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Sickening: ISIS sympathisers took to social media to identify the 10-year-old 'cub fighter' by his alleged nom de guerre Abu Ubaidah. He is said to have died fighting alongside his father in Syria in recent weeks

Pose: Another picture shows him smiling sweetly while wearing an ammunition vest as he stands next to a van that has been converted into an armoured vehicle with a large plank of wood and bull bars

Misled: Abu Ubaidah posing with a man understood to be his father, who militants named as 'Baghdadi'

Several images, which have not been independently verified, emerged on social media this week after a video reporting the deaths of the boy and his father was uploaded to YouTube in September.

The original video - distributed by the pro-Isis media group Al-A'amaq - is understood to have since been removed, but a number of photographs of the boy have since been widely shared by ISIS militants and their sympathisers on social media.

One image shows the boy standing inside a house, grinning as he struggles to hold an assault rifle so large that it threatens to topple him over.

Another picture shows him smiling sweetly while wearing an ammunition vest as he stands next to a van that has been converted into an armoured vehicle with a large plank of wood and bull bars.

Other images show him posing with a man understood to be his father, who militants named as 'Baghdadi'. In those images the boy identified as Abu Ubaidah is seen calmly holding another large rifle while surrounded by bearded men wearing military clothing.

Support: ISIS sympathisers are triumphantly circulating images of a 10-year-old boy they claim has been 'martyred' with while fighting alongside his father in Syria

Smiling: Describing the child as ISIS' youngest foreign jihadist, chilling photographs taken before his alleged death show him grinning at the camera, wearing military fatigues and brandishing a huge assault rifle

HOW THE ISLAMIC STATE HAS LONG GROOMED CHILDREN TO TAKE PART IN SICKENING ACTS OF TERRORISM ISIS - which rebranded as Islamic State earlier this year after establishing a self-described caliphate in the vast swaths of Syria and Iraq under its control - has long groomed children to take part in jihad. The practice was the subject of the second episode of VICE's groundbreaking 'Islamic State' documentary series. The film showed very young boys being asked whether they want to be a suicide bomber or a jihadist when they grow up, and being forced to recite calls for the murder of Western 'infidels'. In the footage, ISIS' PR man Abu Moussa - who has since been killed - describes how every male child under the age of 15 is forced to attend a 'Sharia camp' to be taught the militant group's radical interpretation of Islam. At the age of 16 the boys are sent to a military camp, where they are given intensive training in the art of warfare. After that they are prepared for possible future as either front-line militia or suicide bombers. Advertisement

Last week a 24-year-old Muslim convert admitted taking her infant son to live among Islamic State terrorists in the Syrian city of Raqqa because she believes he will lead a 'better life' under their brutal regime.

Asiya Ummi Abdullah denied that children are unhappy living under the oppressive rule of ISIS' religious fanatics and explained that she felt her three-year-old son's spiritual well-being was better served in the group's de facto capital, where public crucifixions and beheadings are commonplace.

Ummi Abduallah - who had lived in Turkey since her teens but was born in Kyrgyzstan - said moving to the militant stronghold in Syria was in part to shield the young boy from the sex, crime, drugs and alcohol she sees as rampant in her home town Istanbul.

'Who says children here are unhappy?... He will know God and live under his rules,' she said.

Islamic State militants have carried out mass executions, set up slave markets where women are sold for sex for $10 and used child soldiers in what may amount to systematic war crimes in Iraq that demand prosecution, the UN reported last week.

Investigators believe as many as 2,500 women and children have been captured, subjected to sex attacks and then sold for around $10 by extremist militants in Iraq.

In August, ISIS is believed to have taken 450-500 women and girls to the Tal Afar citadel in Iraq's Nineveh region where '150 unmarried girls and women, predominantly from the Yazidi and Christian communities, were reportedly transported to Syria, either to be given to ISIS fighters as a reward or to be sold as sex slaves'.

According to investigators, slave markets have been set up in Raqqa, Syria and the al-Quds area of Maturat in Iraq - partly to attract new Islamic State fighters.