The men are all accused of leaking information to the Iraqi government, which has been advancing on ISIS in the area in recent months.
One of the men, a hospital worker accused of leaking information on injured ISIS fighters is decapitated using explosive wire tied around his neck.
The video names the man as Mohamed Mahmoud Dayih, claiming that he had used his position as a clerk at the Fallujah General Hospital to send information to the Iraqi Interior ministry.
ISIS accused him of handing over information on the medical staff working for ISIS at the hospital, taking pictures of them and giving information on dead and wounded ISIS fighters.
ISIS 2.0 and information war
The video shows him kneeling on the ground while ISIS terrorists tie a blue wire around his neck, evidently packed with explosives.
Seconds later, the camera pans out to show the moment the bomb-rope is detonated, decapitating the man.
The second execution shown is that of two policemen, allegedly arrested by ISIS as they tried to leave Fallujah to pass on information about ISIS fighters to the Iraqi Army.
The men are seen kneeling next to each other wearing orange jumpsuits, before they are shot in the back of the head.
Two others, accused of similar 'apostate' crimes by the terrorist organization are murdered in the same manner in front of the camera.
The sixth victim is named as Sam Faisal Sowaidan, reportedly also a Fallujah policeman who had allegedly been 'spying' on ISIS for the Iraqi Interior Ministry.
ISIS accused him of handing over 'Mujahideen names and places of residence', and executed him by cutting his head off with a knife before displaying his blooded remains.
ISIS is currently fighting an offensive by the Iraqi Army in Anbar Governate, backed up by Coalition airstrikes, with Fallujah being the terrorist group's last stronghold in the state.
As of last month, Fallijah is fully besieged by Iraqi government forces, and the men seen being executed in the video are accused of helping the Army.
The city, located 30miles west of Baghdad is almost completely cut off from the rest of ISIS's self-proclaimed 'caliphate'.
Some three weeks ago, the Iraqi Government reported that 600 ISIS fighters had fled Fallujah, with just an estimated 400 terrorists remaining in the city itself.
The new video appears to be a desperate attempt to show that they still hold power in the city, with ISIS's propaganda machinery writing that it should serve as 'a message to the apostates and their masters that blood for blood and destruction for destruction'.
