New video released by ISIS shows militants smashing what they say are antiquities at a museum in Mosul, Iraq.
Men shove statues off pedestals, and use hammers and drills to destroy what's left.
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 us to destroy these statues, idols and antiquities, we must do it, even if they're worth billions of dollars," he says.
It's not clear from the footage how many of the pieces were originals, versus replicas. Experts are clear in saying, however, the video represents a clear loss.
Qais Hussain Rashid, director general of Iraqi museums at the Ministry of Antiquities and Tourism, said Friday on Iraqiya TV that 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 in June 2014," Rashid said.
He added that Mosul has more than 1,700 historical sites that are potentially at risk.
"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."
"I condemn this as a deliberate attack against Iraq's millennial history and culture, and as an inflammatory incitement to violence and hatred," said Irina Bokova, director-general of UNESCO
, the United Nations cultural organization.
"This attack is far more than a cultural tragedy -- this is also a security issue as it fuels sectarianism, violent extremism and conflict in Iraq
," she said, calling for an emergency meeting of the Security Council to protect Iraq's cultural heritage.
CNN has extensively reported on ISIS' destruction of some ancient and deeply meaningful sites in that country. Officials there have said ISIS has blown up shrines such as the tomb of Jonah.
Its motives are not purely ideological, however; ISIS makes money off looting.
Rashid has told CNN that ISIS sells stolen antiquities to criminals and antique dealers on the black market.
The militant group also allows locals to dig at ancient sites as long as those people give ISIS a percentage of the monetary value of anything found, according to a September 2014 New York Times opinion piece written by three people who had recently returned from southern Turkey and interviewed people who live and work in ISIS-controlled territory.
ISIS' system of profiteering from antiquities thieving is very complicated, the three said, adding that for some areas along the Euphrates River, ISIS leaders encourage semiprofessional field crews to dig.