Athbah (South Mosul)- A large depression in the ground, called Khasfah (an Arabic word for a crack or a hole that opens up in the ground) in the desert south of the northern Iraqi city of Mosul, is believed to be where the dead bodies of ISIS victims are stacked, making it one large mass grave.

Locals believe that the sinkhole is a natural formation caused by a meteorite.

AFP news agency reported locals citing that the ultra-hardline group ISIS has transformed it into a “place of death” after capturing the area in June 2014, using it as an execution site and a mass grave where they disposed victims, according to local residents.

“They would bring them blindfolded, their hands tied behind their backs. The Khasfah would be in front of them, they would make them kneel down, shoot them in the head and push them in,” said Mohamed Yassin, 56, a resident of the nearby town of Hammam al-Alil. A retired soldier, he said he saw people being executed at the site on several occasions after ISIS captured the area in June 2014.

He was in the area regularly, transporting oil from a site just meters away, and said he saw executions there at least six times.

Most of those killed, he said, were policeman, soldiers or government employees, judged guilty for their association with the Iraqi state.

“People became afraid of the place, it became a place of death, a place where you’d be executed.”

Hussein Khalaf Hilal, 73, was taken to the Khasfah by ISIS extremists who accused him of violating their rules by treating people with religious folk medicine.

“They came to the house, they blindfolded me, tied my hands behind my back and took me away in a car with blacked out windows,” he told AFP.

“They took me there because they wanted me to pledge allegiance, to frighten me.

The stories of mass executions match what Belkis Wille, senior Iraq researcher for Human Rights Watch, has heard for months.

“I started hearing about this location about a year ago, in interviews I was doing with people who had fled ISIS control,” she said.

They told her about people who had been executed at the sinkhole, and prisoners whose ISIS guards told them they were taking detainees to the Khasfah to be killed.

Human Rights Watch (HRW) examined satellite imagery that suggested the sinkhole was filling up, and local residents told AFP that ISIS had piled rusted car parts and shipping containers into it, before bulldozing earth on top.

A month after the area was taken from ISIS, the once-cavernous hole now extends just a few meters down for most of its surface.

In the center, there is a smaller, deeper hole, with the carcass of a vehicle lying on top.

The area is strewn with IEDs, both inside and around its perimeter, and is in territory patrolled by Iraq’s Hashed al-Shaabi paramilitaries.

“This is a place where you feel sadness,” said Hashed fighter Abu Ahmed Hassani.

“You think about all the Iraqis who have been executed, from all the sects,” he said.

“They killed children, they killed old people, women, men.”

And the Khasfah is still claiming lives.

On Saturday, a reporter from Kurdish channel Rudaw and three Hashed members were killed at the mouth of its central hole, when an IED detonated.

No exact figures yet exist for the number of bodies that could be buried in the sinkhole.

“The figure that we hear over and over again in interviews is 4,000,” said Wille, stressing the information was as yet impossible to verify.

HRW wants to see Iraq’s government, which has an inter-ministerial team dedicated to dealing with mass graves, carry out an extensive operation to protect and excavate the site.

“We’d want to see that team going up as quickly as possible, marking off the site both to protect it and also to stop people going to a site that’s contaminated,” said Wille.

“After that comes the harder job, which is first collecting the surface remains… for use by forensic experts to start identification, and after that the much harder work of excavating the remains that are below.”

But Hassani said he thought it would be impossible to excavate the many layers of the sinkhole.

“What should happen is that it should be covered over, and become a cemetery for Iraqi martyrs,” he said.