Militants from the Islamic State group have destroyed part of the second-century Roman Theatre in Syria's ancient city of Palmyra.
Maamoun Abdulkarim, the head of the Syrian government's Antiquities Department, said the Tetrapylon -- a group of four sets of four pillars each which were mainly modern replicas -- had also been demolished.
The Boston-based American Schools of Oriental Research posted satellite imagery on its Facebook page showing damage to the two monuments. It said the Roman Theater sustained damage to the stage backdrop, and that only two of the Tetrapylon's columns remain, adding that the monument appeared to have been intentionally destroyed using explosives.
Irina Bokova, the director-general of the UN cultural body (UNESCO), said the destruction was "a new war crime," while Kremlin spokesman Dmitry Peskov said it was a "real tragedy" for the world's cultural treasures.
The IS group recaptured the World Heritage archaeological site from government forces in December, nine months after the extremists were expelled by government troops and allied militias.
The group originally seized Palmyra in May 2015 from the Syrian Army. It is known to have destroyed other monuments before they were forced out by the Russian-backed government offensive.