"The ISIS tied up hands and feet of its militants, put them inside a closed-door car with all the windows rolled up and opened gas hose sent into the car until they died," the Arabic-language media outlets quoted an unnamed source in Mosul as saying.
The ISIS is resorting to different intimidation methods to prevent its own militants from fleeing the battlefield.
In a relevant development on Sunday, the Iraqi forces discovered a mass grave in al-Khalediya Island in Anbar province believed to contain the bodies of 200 ISIS terrorists.
“The mass grave found in al-Malahema region of al-Khalediya Island contains about 200 bodies of the ISIS terrorists,” the Arabic-language media quoted unnamed local sources as saying.
It is not yet clear if the terrorists had been killed in tough battle with the Iraqi joint military forces or executed by their comrades.
AN ISIS MEMBER BEHEADS HIS FATHER IN MOSUL, COLLECTED HIS CLOSE ASSOCIATES TO FILM THE ENTIRE EXECUTION
ISIS DEMANDS THE ACCESSION OF WOMEN TO ITS RANKS; BURNS ALIVE 20 FOR REFUSING
1,400 ABDUCTED YAZIDI CHILDREN TRAINING BY ISIS FOR SUICIDE ATTACKS
AT LEAST 50 BRITISH CHILDREN BELIEVED TO BE LIVING WITH ISIS
In a relevant development last week, the Iraqi army took control of three more strategic villages from the ISIS in Anbar province in Western Iraq, and destroyed the terrorists' military operations room in Albu Jarish region.
The Vinij, Haroun Baraziyeh and Omirieh in the Northwestern part of al-Anbar province are now under the Iraqi army's control.
The ISIS's military operations room in Albu Jarish region was also destroyed by the Iraqi army.
Meantime, tens of ISIS terrorists surrendered themselves in Albu Bali and Albu Obeid regions.
The Iraqi army also killed at least 70 terrorists, including snipers in the military operations in Anbar province on Monday.
The Iraqi joint military forces also destroyed three suicide vehicles in Anbar province over the past two days.
Reports said last week that commanders of the ISIS terrorist group have ordered their forces and family members to leave their last bases and strongholds in Western Iraq as Iraq's military forces are preparing to launch massive military operations in the region, local sources said.
"The Iraqi military forces are preparing to capture the last ISIS strongholds in Western Iraq and the military equipment for these operations have been fully supplied and transferred, and we are waiting for the final order by the joint operations command center to attack al-Khalediya Island and Heet town in the Western parts of al-Anbar province," Head of the Security Committee of al-Anbar province's Council Rajeh al-Issawi said.