Islamic State militants released photos on Tuesday showing the destruction of a Roman-era temple in Syria’s ancient city of Palmyra. UNESCO has called this destruction to be a war crime.

The ancient ruins were destroyed on Sunday, after ISIL seized the site back in May. Photos posted on social media by supporters of the group show militants placing barrels of explosives around the temple.

Palmyra is located 215 kilometers (133 miles) northeast of the Syrian capital, Damascus. The temple of Baalshamin was more than 1,800 years old and one of the most important historic sites in the ancient city. It was listed as a World Heritage site by UNESCO in 1980.

Last week, ISIL beheaded Khaled al-Asaad, 82-year-old Syrian archaeologist who had looked after Palmyra’s ruins for four decades, and hung his body in public.