The destruction of the UNESCO world heritage site was reported two days after the Iraqi antiquities ministry said that IS bulldozed the ancient Assyrian city of Nimrud, and a week after the jihadists released a tape of them smashing artefacts in the Mosul museum.
"The destruction of Hatra marks a turning point in the appalling strategy of cultural cleansing under way in Iraq," UNESCO Director General Irina Bokova said on Saturday.
Hatra is an extremely well-preserved city with a unique mix of eastern and western architecture, located in a desert area about 100 kilometres southwest of the northern jihadist hub of Mosul. "Official sources today reported the destruction of the World Heritage property of Hatra," the organisation said in a statement.
The UNESCO statement did not say when or how Hatra, which was built around 2,200 years ago, was destroyed, nor was any Iraqi official able to provide such details.
Mohammed Nuri, an MP from southern Nineveh province, where Hatra is located, said that "until this moment, there are no confirmed reports that Hatra has been destroyed." "Hatra is somewhat isolated, and residents are not nearby," he said.
"I have not heard of someone who physically saw the destruction taking place." A statement from Iraq's tourism and antiquities ministry also condemned the destruction of the city, but it only cited media reports and did not directly confirm the incident.
However, after smashing statues in the Mosul museum and at an archaeological site in the city, IS militants reportedly warned a guard that they would go on to destroy Nimrud and Hatra. But razing the entire site of Hatra, whose thick walls and large buildings withstood two Roman invasions in the 2nd century, would be no small undertaking.
UNESCO describes Hatra as "a large fortified city under the influence of the Parthian Empire, the capital of the first Arab kingdom, and bearing the roots of Islamic Arab cities."
"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 extremist groups," Bokova said. She co-signed the statement with Abdulaziz Othman Altwaijri, Director General of the Islamic Educational, Scientific and Cultural Organisation.