ISIS execution screenshot
'The Bulldozer' was an Isis executioner, who killed prisoners who had been sentenced to death Screenshot

Disturbing footage of an Islamic State (Isis) courthouse has been released showing where some of the cruellest and most inhumane punishments in the world were handed out.

Defendants held in the building in the Iraqi city of Fallujah, a former IS (Daesh) stronghold, were locked in tiny, iron cages before standing trial before extremist judges.

The cramped human cages were designed in different sizes to allow defendants to either stand, kneel or curl up, depending on their crime.

The prisoners were all held in the same decaying room next to the courtroom where many prisoners were sentenced to death.

The men and women standing trial, who were often "innocent locals" or security personnel, were only released from their cells to stand trial for their so-called crimes against Islamic State or breaking the terror groups laws.

They would then be dragged to the courtroom, which bears a striking resemblance to a Western courthouse complete with judge's bench and rows of chairs.

However, in a marked difference, the courthouse walls were adorned with the Islamic State's signature black-and-white flag.

As part of the proceedings, judges would try defendants based on the group's extremist ideology.

Discovered by Iraqi soldiers, it is believed the courthouse was used by IS as recently as June, after which the group was finally driven out of Fallujah.

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IS had occupied the city in Al Anbar since January 2014.

The footage of the building, released by RT Arabic – a branch of the Russia's state-funded TV news network – shows photos of former defendants and information on their crimes and trials.

Standing at the site, Iraqi Army Brigadier Jalil Abdulredha, told NBC: "They used to imprison locals in iron cages like animals.

"They made different shapes of cages for different positions, such as kneeling and standing. This shows the brutality of this terrorist organisation."