Brutal terror regime releases new video showing victims murdered gruesomely, including being locked in car and shot by RPG.

The brutal Islamic State (ISIS) group has spread horror by callously beheading victims and burning them to death - on Tuesday the terror group reached a new low by unveiling gruesome new ways to murder.

In a seven-minute video from ISIS's Nineveh branch based in its stronghold of Mosul, the terrorists reinvented their horrific methods of murder on three separate batches of helpless victims.

At the start of the clip, several men in the orange jumpsuits worn by victims in ISIS videos are locked in an Opal saloon car in the desert, before a masked ISIS terrorist fires an RPG (rocket-propelled grenade) launcher at the vehicle from point-blank range.

The car explodes in flame, burning to death the victims trapped inside.

If the clip started with incendiary flames, the most horrific moment may have been what follows next, as water is used in a twisted way to drown five men in orange jumpsuits.

The group are forced to talk on camera about the crimes of "spying" they were evidently accused of, before being locked in a massive metal cage and lowered into a swimming pool.

At first the group stand straight with their legs bound until the cage is lowered in the water. As the water raises ever higher the men become visibly panicked, praying and pacing the tiny cell before the water reaches over their heads.

The video then switches to expensive underwater cameras attached to the bars of the cage to show the men thrashing hopelessly underwater before losing consciousness and drowning.

The cage is then lifted out of the water again, showing the drowned men lying foaming at the mouth.

After the gruesome interlude of watery deaths, the film returns to fiery explosions as another set of seven victims are forced to talk on camera before being led out into a field.

There explosive cables are tied around all of their necks as they are forced to kneel in a line. The cables are then detonated, decapitating and horrifically maiming the victims, and all of the gore is captured in HD quality footage.

ISIS has used such gruesome films in the past both to recruit jihadists from around the world as well as to strike fear and terror into their opponents.