The head of the UN cultural organisation on Wednesday called for a campaign against the "culture cleansing" being carried out by Islamic State jihadists.

"Extremists don't destroy heritage as a collateral damage, they target it systematically to strike societies at their core," Irina Bokova said in a speech at the Chatham House think tank in London.

"This strategy seeks to destroy identities by eliminating heritage and cultural markers," she said.

Several archaeological sites have been attacked by IS jihadists in Iraq and Syria and their recent takeover of an area including the ruins of the ancient city of Palmyra in Syria sparked worldwide concern.

In April, the IS group released a video in which militants can be seen using rifles and sledgehammers to destroy artefacts at the ancient fortress city of Hatra, famed for its unique blend of eastern and western architecture.

UNESCO on Wednesday named 2,000-year-old Hatra as one of its 'Heritage in Danger' sites, joining the likes of the US Everglades and the Old City of Jerusalem.

The site was listed due to the "destruction inflicted.. by armed groups," UNESCO said in a statement.

Earlier the militants also damaged the site of Iraq's ancient Assyrian city of Nimrud and destroyed dozens of pieces from the museum in Mosul.

"I think the growing awareness that hard power will not be enough to defeat violent extremism is gaining ground. We need also soft power," Bokova said.

"Culture should be part of our response to violent extremism," she said.

UNESCO is currently meeting in Bonn in Germany for its 39th committee session until July 8 and will consider at least 36 natural and cultural sites vying to get World Heritage status.

It was at the meeting in Germany that Hatra received its special classification.

The organisation has launched a campaign called "United Heritage" to defend historical sites under threat from jihadists and to counter militant propaganda.