Meeting in Bonn, Germany, UNESCO delegates said the Daesh attacks on sites such as Iraq's ancient city of Hatra recalled the "mindless destruction" by other Islamist extremists in Bamiyan, Afghanistan, in Mali's Timbuktu and elsewhere.
The UN Educational, Scientific and Cultural Organization said "intentional attacks against buildings dedicated to religion, education, art, science or charitable purposes and historic monuments may amount to war crimes".
In April, the Daesh group released a video in which militants can be seen using rifles and sledgehammers to destroy artefacts at Hatra. 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.
The UN body also expressed its "deep concern" that Daesh militants could destroy the World Heritage site of Palmyra in Syria, which they captured in May and have extensively mined.
UNESCO said that World Heritage sites in conflict-torn Afghanistan, Iraq, Libya, Mali, Syria and Yemen also faced heightened threats through "illegal excavations, organised looting and trafficking of cultural objects".
UNESCO stressed it denounces the destruction and looting of cultural objects "used as a tactic of war and as a source to fund terrorism", calling for steps against the illegal trade of antiquities and heritage objects from conflict areas.
UNESCO is meeting in Bonn for its 39th committee session until July 8 and will consider at least 36 natural and cultural sites vying to get World Heritage status.