"It's tragic to see this destruction," William Webber, from the UK-based Art Loss Register
, told CNN. "Each time you see this you think it can't happen again, but it does. Now other Greco-Roman treasures are at risk around Mosul in Iraq, as well as other artifacts in Palmyra and Raqqa in Syria."
The video shows men taking sledgehammers to statues, and hammers and drills to the treasures. Qais Hussain Rashid, director general of Iraqi museums at the Ministry of Antiquities and Tourism, said Friday on Iraqiya TV he believed most of the artifacts shown in the ISIS video were real -- including a famed, millennia-old winged bull that's seen being defaced with a drill.
"Mosul Museum has 173 original pieces, and there were preparations to reopen the Mosul Museum before ISIS invaded the city on June 2014," Rashid said.
He added that Mosul has more than 1,700 historical sites that are potentially at risk.
An unnamed militant offers the following explanation: "These antiquities and idols behind me were from people in past centuries and were worshiped instead of God.
"When God Almighty orders to us destroy these statues, idols and antiquities, we must do it, even if they're worth billions of dollars."
CNN has extensively reported on ISIS' destruction of some ancient and deeply meaningful sites in Iraq. Officials there have said ISIS has blown up shrines such as the tomb of Jonah
'Depressing and shocking'
"If you're going to eradicate someone's identity the best way is to eradicate their art," Webber said. "They see this art as blasphemous because it portrays deities. In areas of Syria, ISIS is also attacking anything that's pre-Islamic or that they don't agree with in Shia areas or in Christian churches."
Most of the sculptures being destroyed were from the Assyrian period [roughly 2500 to 605BC], Webber said. Militants were pulling them over and smashing them; bigger relief pieces were being smashed with hammers. "It's very depressing and shocking. If they have control of the whole museum they could destroy the whole lot, or sell some pieces such as coins, tablets and cylinder seals."
It's unclear from the footage how many of the pieces were originals, versus replicas. Webber said he hoped that some of the items were copies rather than the real thing, but added that at least some of those shown in the video were genuine. "Much of the material in the museums was made out of limestone or fragile stone, so if you threw it to the floor it might look as though it was made of plaster of Paris, but really it's just fragile. It's tragic to see it."
Webber said that following vandalism at provincial museums in the wake of the first Gulf War, many antiquities were moved to Baghdad, where they were ransacked in 2003. "It appears that they had not been moved from this museum in Mosul."
Other experts agreed that the items destroyed appeared to be genuine. "On repeated viewing of that very grainy video, we now suspect that there (were) far more originals in the museum than I first thought," said Eleanor Robson, chairwoman of the British Institute for the Study of Iraq.
"Whilst there was indeed a program to relocate antiquities to safekeeping in Baghdad, it looks now as though it didn't reach that particular museum."