Story highlights Director general of Iraqi museums says Mosul Museum had 173 original pieces

It's not clear from the footage how many of the pieces were originals, versus replicas

UNESCO chief: "This attack is far more than a cultural tragedy -- this is also a security issue as it fuels sectarianism"

Irbil, Iraq (CNN) They take sledgehammers to statues with an uncommon gusto -- destroying in seconds what may have survived centuries.

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.

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