The United Nations' cultural body on Saturday condemned the "destruction" by the Islamic State jihadist group of Hatra, a stunning Roman period ancient fortress city in the Iraqi desert.

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.

Hatra is an extremely well-preserved city with a unique mix of eastern and western architecture, located in a desert area about 60 miles (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.

- Arab capital -

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 (ISESCO).

The jihadists try to justify the destruction by saying the statues and sites are idolatrous, but experts say they traffic antiquities to fund their self-proclaimed "caliphate" and destroy only those pieces that are too bulky to be smuggled.

The timing of the attacks also indicates that they are more for propaganda than religious purposes, as there were more than eight months in which the militants controlled the areas where the sites are located.

"This is part of their propaganda, it is designed to shock us," said Eleanor Robson, professor of ancient near eastern history at University College London.

- Powerless -

The Islamic State group, which conquered nearly a third of Iraq virtually unopposed nine months ago, has built a reputation as the most violent group in modern jihad by beheading and crucifying its victims in public or on tape.

But Iraq's allies, led by the United States and Iran, have since come to the rescue and helped organise a major counter-offensive that is steadily shrinking IS' footprint.

After being forced out of the province of Diyala earlier this year, the jihadists are now fighting off a huge assault on the city of Tikrit as government and allied forces continue to work their way north towards the main IS stronghold of Mosul.

The spate of attacks on heritage sites in a region described as the cradle of civilisation has sparked a global outcry and drawn comparisons with the 2001 dynamiting by the Taliban of the Bamiyan buddhas in Afghanistan.

Hatra is one of only four UNESCO world heritage sites in Iraq and one of its most famous archaeological treasures.

"It was ruled by Arab kings and thrived as a major staging post along the famous Silk Road of ancient times linking the East to Palmyra (in Syria) and further on to the shores of the Mediterranean," said Ihsan Fethi, an Iraqi architect and heritage expert.

The archaeological world had been resigned to the prospect of Hatra's destruction.

"Now we are confronted with our worst fears -- a senseless and fanatical campaign of destruction and about which we can do very little," Stuart Gibson, a UNESCO expert on museums, had told AFP before reports of Hatra's destruction.

Iraq minister says coalition must defend heritage sites
Baghdad (AFP) March 8, 2015 - The US-led coalition carrying out air strikes against the Islamic State group must try to protect archaeological sites being destroyed by the jihadists, Iraq's tourism and antiquities minister said Sunday.

IS smashed priceless artefacts at the Mosul museum, then bulldozed the city of Nimrud, which was founded in the 13th century BC.

The jihadists may now have turned their attention to the extremely well preserved fortress city Hatra, which is more than 2,000 years old and a UNESCO world heritage site, with the United Nations condemning its reported "destruction".

"The sky is not in the hands of the Iraqis, the sky is not in our hands. Therefore, the international community must move with the means it has," Adel Fahad al-Shershab told journalists in Baghdad.

"We request aerial support," Shershab said.

Asked specifically if he wanted coalition strikes to protect archaeological sites, he responded: "What I request from the international community and the international coalition is to carry out air strikes against terrorism wherever it is found."

The attacks on Iraq's archaeological heritage took place in IS-held areas in the northern province of Nineveh, where Iraq does not have security forces that are able to respond on the ground.

Targeting militants destroying archaeological sites would be a departure for the coalition, which is waging a campaign of strikes aimed at weakening IS military capabilities in Iraq and neighbouring Syria.

- 'It was expected' -

The coalition announced that it had carried out 12 air strikes in Iraq from Saturday to Sunday morning, including two near Mosul that reportedly destroyed an IS unit and two "excavators", but it was unclear if these were involved in attacking historic sites.

"The site of Hatra is a site in the desert where it is possible to see any infiltration" from the air, Shershab said of the ancient city, which features a unique blend of eastern and western architecture.

"It was expected that they (IS) would destroy it," he said.

But it remains unclear whether large-scale destruction was carried out at Hatra, whose thick walls and large buildings withstood two Roman invasions in the 2nd century AD.

Shershab said his ministry had not been able to officially confirm what had happened because the area is held by IS.

The jihadists spearheaded a sweeping offensive last June that overran large areas north and west of Baghdad, and Iraqi forces backed by the US-led coalition and Iran are battling to push them back.

IS tries to justify the destruction of antiquities by saying they are idolatrous, but experts say the group traffics in them to fund its self-proclaimed "caliphate" and destroys only those pieces that are too bulky to be smuggled.

Shershab echoed the point on Sunday: "They say 'it is haram' (forbidden by Islam). At the same time they are selling (artefacts) and benefiting financially."

The timing of the attacks suggests they are more for propaganda purposes than a matter of religious conviction, as the militants have controlled the areas where the sites are located for close to nine months before acting.