The Islamic State terrorist group recently carried out a grotesque form of punishment, killing six men accused of being "spies" by boiling them to death in vats of tar.
According to the Daily Mail, the Muslim extremists carried out the horrific executions in public at an ISIS command center in al-Shora in Iraq, "with the aim of inciting fear among the citizens".
A source told Iraqi News: "ISIS executed six persons in Mosul for collaborating with Nineveh Operations Command. The death sentence was issued [by an] Isis Sharia Court.
"The six persons were placed inside tanks containing boiling tar and the execution was carried out in one of Isis headquarters at al-Shora. The execution took place... with an aim of inciting fear among the citizens."
Media activist Abdullah al-Malla told the Kurdish news site ARA News that hundreds of citizens were present and forced to listen as an IS 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 IS official was quoted as saying. "The Caliphate [Islamic State] will show no mercy to such traitors."
The gruesome deaths come amid mounting evidence that the terrorist group has been using mustard gas on the frontline in Iraq, leaving troops with severe injuries, including blisters on their skin and badly damaged lungs. Used with lethal effectiveness in World War One, mustard gas causes severe delayed burns to the eyes, skin and respiratory tract.
Hamish de Bretton-Gordon, a specialist in biological and chemical warfare, told Reuters that Islamic State fighters may have developed their own chemical weapons capability, and could be preparing to use it again.
"I'm pretty convinced that the mustard IS are using in Iraq is made by them in Mosul," he said, referring to the main city in northern Iraq, which Islamic State fighters have occupied since 2014. "They have all the precursors at hand from the oil industry and all the experts at hand to do it."
Meanwhile, on Wednesday, a security source in Nineveh revealed that an airstrike in Mosul carried out by the US-led international aviation killed at least 50 ISIS men and destroyed a chunk of their vehicles and other belongings.
Sharing details about the incident, the source seeking anonymity said, "International coalition aviation jets today bomb ISIS headquarters at Masaref, Kahera, Ghabat and Somer in central Mosul, killing 50 men of the outfit."
"The airstrike also destroyed a number of ISIS headquarters and 22 vehicles of the outfit," the source further added.
Speaking to CNN on Wednesday, a Peshmerga commander on the front lines revealed Iraqi forces expect to push back ISIS forces from Mosul in six weeks to two months.