Iraqi Counter Terrorism Services soldier is seen during a battle between CTS and ISIS militants in western Mosul, Iraq, April 25, 2017.

Iraqi forces on Tuesday launched a fresh push southwest of Mosul to retake the Hatra area, which includes a UN-listed World Heritage site, a statement said.

The operation marks the latest phase of an offensive launched by the Hashed al-Shaabi (Popular Mobilisation) paramilitary forces in parallel to the main assault on Mosul begun six months ago.

The Hashed forces, dominated by Iran-backed militias, have focused their efforts on a front southwest of Mosul which aims at retaking the town of Tal Afar as well as desert areas stretching to the border with Syria.

“Hashed al-Shaabi forces launched Operation Mohammed Rasool Allah aimed at liberating Hatra and neighboring areas,” the organization said in a statement.

It said that five villages had already been retaken from the ISIS group on Tuesday and that Hashed engineering units were clearing the road to Hatra of explosive devices.

Hatra, known as Al-Hadhr in Arabic, was established in the 3rd or 2nd century BC and became a religious and trading center under the Parthian empire.

Its imposing fortifications helped it withstand sieges by the forces of two Roman emperors: Trajan in 166 AD and Septimus Severus in 198.

Hatra finally succumbed to Ardashir I, the founder of the Sassanid dynasty, a few decades later, but the city remained well-preserved over the centuries that followed.

Hatra left its mark on pop culture as the location for the opening of horror film “The Exorcist”, which was shot there in 1973.

The militants damaged parts of Hatra after taking over a third of Iraq in 2014, as part of a heritage destruction campaign that also saw them vandalise Mosul museum, blow up shrines and damage the ruins of the ancient city of Nimrud.

The militants see such destruction as a religiously mandated elimination of idols – but they also have no qualms about selling smaller artefacts to fund their operations.

The full extent of the harm to Hatra remains unclear, but the site risks further damage during the military operation to retake it.