A video released on Thursday by ISIS shows members of the terrorist organization destroying ancient Assyrian artifacts at Iraq’s Mosul Museum and the nearby Nineveh archaeological site. The disturbing footage shows men toppling statues, smashing them with sledgehammers, and breaking them apart with drills and jackhammers.

“The prophet Muhammad commanded us to shatter and destroy these statues,” a spokesman for ISIS says at the beginning of the video, according to a translation by the Middle East Media Research Institute. “This is what his companions did later on when they conquered lands. Since Allah commanded us to shatter and destroy these statues, idols, and remains, it is easy for us to obey and we do not care [what people think], even if this costs billions of dollars.”

The video begins inside the Mosul Museum, which ISIS has occupied since last summer, when it first threatened to destroy the collection. Considered the country’s second most important museum, after the Iraq Museum in Baghdad, the institution houses many artifacts dating back to the city’s heyday as the capital of the Assyrian Empire. The museum, which like many of Iraq’s institutions was looted after the US invasion in 2003, was on the verge of reopening following an extensive renovation when ISIS took control of Mosul in June 2014.

The latter portion of the video shows the destruction of sculptures at the Nineveh archaeological site directly across the Tigris river from Mosul. While many of the large-winged figures and bas-reliefs that used to adorn the ancient site have made their way into the collections of the West’s most prestigious museums — including the Metropolitan Museum, the British Museum, and the Louvre — others remained at the site, whose ancient gates have also been preserved. The ISIS video shows men using drills and sledgehammers to destroy at least three tall statues of winged and bearded figures, some of which date back to the 7th century BCE. The large sculptures adorned the gates of the ancient city.

According to an ISIS spokesperson at the beginning of the video, the artworks were “the idols of peoples of previous centuries, which were worshiped instead of Allah.” The group has been known to smuggle antiquities out of Iraq and Syria and sell them to fund its operations, but the decision to destroy rather than export the invaluable Mosul artifacts is part of ISIS’s mission to decimate shrines, buildings, and artworks that it views as heretical to its theology.

In a statement this afternoon, Thomas P. Campbell, the director of the Metropolitan Museum, expressed sadness and anger over ISIS’s actions:

Speaking with great sadness on behalf of the Metropolitan, a museum whose collection proudly protects and displays the arts of ancient and Islamic Mesopotamia, we strongly condemn this act of catastrophic destruction to one of the most important museums in the Middle East. The Mosul Museum’s collection covers the entire range of civilization in the region, with outstanding sculptures from royal cities such as Nimrud, Nineveh, and Hatra in northern Iraq. This mindless attack on great art, on history, and on human understanding constitutes a tragic assault not only on the Mosul Museum, but on our universal commitment to use art to unite people and promote human understanding. Such wanton brutality must stop, before all vestiges of the ancient world are obliterated.

Update, 7:11pm ET: Archaeologists told the UK’s Channel 4 that many if not all of the sculptures shown being smashed at the Mosul Museum are in fact replicas of the originals, most of which were moved to the Iraq Museum in Baghdad in anticipation of a situation such as this one.