ISIS boils 6 men alive in vats of tar

ISIS drowns its victims in a pool, one of several execution methods used by the militant group.YouTube

Last time, they used nitric acid. This time, it's boiling tar.

In its latest act of sheer savagery, the Islamic State (ISIS) executed six men in Iraq accused of collaborating with the U.S.-led coalition and Kurdish forces by placing them in vats of boiling tar, Iraqi News reports.

A source told the news agency that the ISIS officials decided on the new torturous execution method to intimidate local residents, hundreds of whom watched the brutal act outside the ISIS headquarters in Mosul.

According to witnesses, an ISIS official read the charges against the men before the execution was carried out.

"Those mercenaries have cooperated with the crusader coalition and the Peshmerga in order to destroy the Caliphate territory and kill innocent Muslims in the name of freedom and democracy," the ISIS official was quoted as saying. "The Caliphate [ISIS] will show no mercy to such traitors."

Last May, the ISIS reportedly executed 25 people accused of spying by dissolving them alive in nitric acid.

"ISIS put the citizens in a large tub containing nitric acid inside one of its headquarters," a source told Iraqi News, adding that the victims were tied with ropes and lowered into the acid "till the victims' organs dissolved."

That same month, Kurdish commander Hasan Khala Hasan told the Iranian-based AhlulBayt News Agency that ISIS executed a number of its own commanders for failing to "accomplish their chief duties."

Hasan said the leaders were tied to trees before they were savagely ripped apart and killed by ferocious dogs let loose on them.

The barbaric group has also used water, guns, knives, wire and fire to execute its victims.

Lately, however, ISIS officials appeared to have taken a liking to boiling their helpless victims to death, according to the Christian Post.

Just last month, the militant group reportedly executed seven of its own fighters who fled the battlefield in Iraq by tying them up and boiling them alive in a giant cauldron of water.

About 33,000 deaths have been linked to ISIS and ISIS-affiliated groups since 2002, according to a recent report from the National Consortium for the Study of Terrorism and Responses to Terrorism at the University of Maryland.