Iraqi popular forces have discovered another mass grave located northwest of the city of Mosul, Fars news agency reported on Sunday.

As the Iraqi army forces and their allies were continuing their operation to push back ISIS terrorists from Mosul, Hashd al-Shaabi's Second Brigade found dead bodies of some 500 civilians in Badoush prison.

The victims were executed by ISIS after the terrorist group took control of Badoush prison.

It came nearly three months after the Iraqi army forces found a mass grave, with tens of victims of ISIS executions buried in a village which was recently retaken by the Iraqi government.

The site was reported to contain dead bodies of at least tens of ISIS’s victims who were buried near Mosul in Hammam al-Alil, which is the last major settlement along the Rigris River before Mosul.

The victims were members of the police.

Last month, the Iraqi forces said that it had found the largest mass grave in Iraq with dead bodies of thousands of security forces killed by ISIS.

The mass grave was located 400 kilometers north of the capital Baghdad.

The Khasfa sinkhole is the resting place of an estimated 4,000 victims, according to a report by the British daily newspaper The Daily Telegraph.