The warped jihadis killed the children in an industrial dough kneader — sometimes in front of their horrified mums and dads — in a bakery in Duma in Syria.
A chilling new report states one Syrian woman, Alice Assaf, spoke of "Christians being killed and tortured".
She added children are being beheaded in front of their parents.
She continued: "Our neighbour came in and said 'Umm Issa, they have taken many girls, about 300 girls. They were taken to Duma. Many of them were Christians and few were Alawites.'
"At the bakery there were six young people who were working there. We knew them. They were burned in the oven, six well-framed
men."
"Then there were 250 children. They were put in the dough mixer, they were kneaded. The oldest of them was four years old," Ms Assaf told advocacy charity Roads to Success.
“Then there were 250 children. They were put in the dough mixer, they were kneaded. The oldest of them was four years old”
ISIS meanwhile continues to wipe out Christians in the Middle East, targeting believers in Iraq and Syria.
The latest damning report, by charity Open Doors UK, found Christians in the region have been taken hostage, church leaders assassinated, homes and businesses destroyed and women and girls forced into sexual slavery.
A spokeswoman from Open Doors UK said: “Horrific stories such as these are sadly all too familiar to those who have encountered Daesh (ISIS).
"Open Doors local partners in Syria and Iraq are providing trauma counselling to help victims of abuse begin to heal following their terrible experiences, as well as providing practical support.”