ISIS forces have destroyed hundreds of thousands of rare books and manuscripts in the Central Library of Mosul, Iraq.
The head of UNESCO, Irina Bokova, stated her concern over "one of the most devastating acts of destruction of library collections in human history.
"This destruction marks a new phase in the cultural cleansing perpetrated in regions controlled by armed extremists in Iraq. It adds to the systematic destruction of heritage and the persecution of minorities that seeks to wipe out the cultural diversity that is the soul of the Iraqi people."
Images also emerged of militants destroying ancient artworks in the city's Nineveh Museum. One man in the video states: "The Prophet ordered us to get rid of statues and relics, and his companions did the same when they conquered countries after him".
The devastation echoes the dynamiting of the monumental Bamiyan Buddhas in Afghanistan in 2001.
ISIS is founded on an extreme interpretation of Sunni Islam and views even followers of other branches of Islam as heretics. Thus any form of religious idolatry, no matter how old or historically significant, cannot be allowed to exist.
The lack of stability in the region is likely to lead to the widespread theft of artefacts, prompting UNESCO to warn auction houses to be extra vigilant.