Isis has executed at least 25 people by dissolving them in acid, according to reports in Iraq.
The horrifying incident happened in Mosul, northern Iraq with the victims were accused of being spies for Iraqi Government forces.
Iraqi News reported that the 25 people were tied together with a rope before being thrown into a massive basin where they were exposed to Nitric acid.
The execution was conducted in a public square as a warning to others.
"ISIS terrorist members executed 25 persons in Mosul on charges of spying and collaborating with Iraqi security forces," Iraqi News said in a statement.
"ISIS members tied each person with a rope and lowered him in the tub, which contains nitric acid, till the victims organs dissolve."
Nitric acid is highly destructive to the human body and is normally used in the manufacturer of fertilizer and explosives and in the reprocessing of spent nuclear fuels.
When it comes into contact with the skin, it leaves severe chemical burns and blisters.
It is the latest in a series of gruesome executions the terror group have conducted, thought to be in response of losing significant territory in Iraqi. The Pentagon estimates that the group has lost 30-35pc of its territory after strikes and counter-attacks in recent months.
Yesterday, it was reported that Islamic State militants are gearing up for a campaign of bomb attacks on large crowds in France, host to next month's Euro 2016 soccer championships.
Rare remarks by Patrick Calvar, the head of France's DGSI internal intelligence agency, to the parliament's defence committee spelled out "a new form of attack ... characterised by placing explosive devices in places where there are large crowds and repeating this type of action to create a climate of maximum panic.
"Clearly, France is the most threatened and we know that Daesh (Islamic State) is planning new attacks," Calvar told the committee on May 10, according to a transcript of his testimony released to the media on Thursday.
The comments came six months after militants killed 130 people in coordinated assaults on cafes, bars, a football stadium and a music hall across Paris.