The guard witnessed ISIS fighters use female prisoners as sex slaves after the terror group declared a caliphate in 2014.
Identified only as Nizar, the guard said hundreds of women were arrested and separated from their children to become sex slaves, like reported by express.co.uk.
Nizar, told the International Centre for the Study of Violent Extremism, life under ISIS in Syria was good to begin with.
He said: “When they first came, things were very good. It really felt like Islam. We started going to the mosque. A sheikh would give lessons in the Koran.”
Nizar says he and his wife were told ISIS was right and there would be no injustice under their regime.
He started work at the religious police’s prison and was in charge of guarding prisoners – men and women- serving time for breaking Sharia law.
Nizar said: “They were imprisoned, whipped and beaten. After two or three days they were released.”
Up to 500 Yazidi women were also held at the centre.
He said: “When I walked down the corridor, I was shocked looking at all these women.
“Some of the Yazidi girls would cry.”
Nizar said the situation escalated when ISIS fighters from outside Syria and Iraq heard new female prisoners had arrived.
The fighters would cheer and choose a woman each to be their sex slave or force them into marriage, with the prisoners terrified if they did not comply they would be executed.
He said: “So the prison warden would bring 10 foreign fighters at a time because they could not be brought in all at once. We would guard the doors and they would go in and choose a captive woman.”
As ISIS’s brutality was laid bare Nazir said he struggled to cope and the case of a 15-year-old girl forced him to escape.
A Sudanese ISIS militant picked the teenage girl as his slave and raped her in his cell.
Nizar said: “She started bleeding badly. An ambulance came to take her. The girl had internal bleeding and died from the injuries.
“I was warned not to speak about the incident. They said: ‘Captives are captives. Do as you please with them’.”
Nizar, who now lives in Turkey with his wife, plotted his escape from Syria after being granted three days leave.
Afraid of suffering the same fate as the sex slaves, Nizar’s wife persuaded him to flee.
The guard was granted three days of leave allowing the couple to plot their escape to Turkey.
It comes after former ISIS captives revealed how the jihadis threatened to kill them unless they converted when ISIS invaded Mosul in Iraq.
Jandark Behnam Mansour Nassi, 55, and her son, 16-year-old Ismail, saw ISIS child fighters execute prisoners and jihadis stone a woman to death after being robbed and captured by the terror group.
ISIS threw Ismail into prison and said they would shoot him unless he converted.