Three hostages freed last month from an ISIS compound in Northern Iraq have shared details of their experiences on Islamic State's death row.

Kurdish forces, supported by US special operations forces, liberated nearly 70 IS-held captives on 21 October from an IS prison near Hawija, Iraq. They were acting on intelligence that ISIS was going to execute dozens of Iraqi prisoners.

Delta Force Master Sgt Joshua Wheeler lost his life in the operation, the first US soldier publicly known to be killed in the fight against IS.

Speaking to Reuters, former Iraqi police officer Saad Khalaf Ali shared that his execution date was scheduled for 22 October, the day after the raid occurred.

Ali had been put on death row after he confessed to informing Kurdish and Iraqi forces about IS militia positions.

He managed to avoid confessing while they tortured him physically, but confessed to the crime after they threatened to kill his family.

They would suffocate him with a plastic bag until he became unconscious before subjecting him to shock torture. The electric current through his body would bring him back to consciousness.

When they threatened to kill his family, "I confessed to everything," he said.

Ali, 32, was then sentenced to death by an IS judge.

He recalled hearing a bulldozer digging a trench outside his cell days before his scheduled execution. The next day other prisoners were taken outside, shot and killed.

He remembers hearing specifically 26 gunshots.

The day before his execution, Ali wrote his last wishes onto a Muslim prayer timetable. He asked his nephew to take care of his family.

He also wrote the name of the man who betrayed him to IS so that his nephew could avenge his death.

As Ali's execution was merely hours away on the night of the rescue, he was up late crying until he heard the rescue helicopter. Minutes later, the door of his room was opened by a commando with an M16 rifle.

"Don't be afraid, we have come to liberate you with the Americans," Ali recalled the Kurdish commando saying.

Ahmed Mahmoud Mustafa and Mohammed Abd Ahmed were also held as hostages by IS.

They described how their captors forced them to pray five times a day and read Islamic lessons prepared by ISIS.

Mustafa was held in a windowless room with 38 other prisoners; there was only just room for each of them to lie down.

The men detailed how they were forced to watch beheadings on large screens, and the punishment they faced when they tried to look away.

Ahmed said when he tried to turn away from a particular video, he was beaten on the head.

They had both had experiences of ISIS before their imprisonment in Hawija. Mustafa had been arrested four times before this instance, because someone he had a personal issue with was well connected with ISIS.

Ahmed said he was once whipped 50 times for criticising militants and threatened that if he did it again they would slice off his tongue.

Both men were imprisoned for espionage, a crime punishable by death under ISIS' Sharia Law.

Mustafa was betrayed by his cousin and Ahmed confessed under torture, concluding that his inevitable death would come sooner if he confessed.

When Ahmed was sentenced to death, the militants asked whether he would prefer to be decapitated from behind or in front.

"It's up to you," Ahmed replied.