Iraqi children run in front of a temple in the historic city of Hatra in this 2002 picture.

The ruins of Hatra, an ancient city in Iraq that once withstood attacks from the Roman Empire, have been destroyed by ISIS militants, according to local officials and the United Nations.

Officials with Iraq's tourism and antiquities ministry told the BBC that the extent of damage to the UNESCO world heritage site is not yet clear, but there are indications it has been demolished.

A joint statement condemning the destruction was released by the Director-General of the U.N.'s cultural body UNESCO, Irina Bokova, and Dr Abdulaziz Othman Altwaijri, Director General of the Islamic Educational, Scientific and Cultural Organization (ISESCO).

"The destruction of Hatra marks a turning point in the appalling strategy of cultural cleansing underway in Iraq," the pair said. "This is a direct attack against the history of Islamic Arab cities, and it confirms the role of destruction of heritage in the propaganda of extremists groups."

Hatra, which stood from about 400 B.C. to 300 A.D., was an important staging post on the famed oriental silk road. It is considered one of the most important sites from ancient Mesopotamia.

Kurdistan Democratic Party official Said Mamuzini told the BBC that ISIS militants were using explosives and bulldozers to destroy the site.

"The city of Hatra is very big and many artifacts of that era were protected inside the site," he said.

He noted that militants had also plundered gold and silver artifacts from the site.