ISIS has also recruited, trained and used children on the battlefield.
Another teenager has also described his horrific experience how he fought and killed for the al-Qaeda-linked al-Nusra Front at the age of just 15, and that when he switched to ISIS he found 13-year-olds being indoctrinated.
In the video, two masked men, equipped with knife and AK.47 can be seen beating blindfolded Ahmed, who is hanging from ceiling by his arms.
From the safety of neighbouring Turkey, he relived the nightmare.
"I thought about my parents. I thought about my mum," he said.
"I thought I was going to die and leave my parents, my siblings, my friends, my relatives all behind. I thought I was going to die."
"They started lashing me, electrocuting me in order to confess. I told them everything".
In the ISIS-controlled northern Syrian city of Raqqa, Ahmed had sold bread to make a living.