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 sympathizers 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.
Several images emerged on social media this week after a video reporting the deaths of the boy and his father was uploaded to YouTube in September.
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.
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' 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.
ISIS 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 fighters.