The United Nations cultural organisation July 1 called for a campaign against the "cultural cleansing" being carried out by the Islamic State.
IS has destroyed archaeological treasures in Iraq, Syria, Libya, and Yemen, including two mausoleums in the recently captured ancient city of Palmyra.
IS' destruction of the 2,000-year-old fortress city of Hatra in Iraq with sledgehammers, seen in a video this spring, prompted UNESCO this week to put Hatra on a list of 'Heritage in Danger' sites, joining the Old City of Jerusalem and other threatened archeological wonders.
"Extremists don't destroy heritage as a collateral damage, they target it systematically to strike societies at their core," said UNESCO's Director-General Irina Bokova.
UNESCO has launched a campaign called "United Heritage" to defend historical sites under threat from miltiants.
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.
Such acts are motivated by "ignorance and criminal stupidity," said Bokova. "Culture should be part of our response to violent extremism."