BAGHDAD — Islamic State extremists trucked away statues as they damaged the irreplaceable remains of an ancient Assyrian capital, a local resident and a top U.N. official said Friday.

Nimrud, a nearly 3,000-year-old city in present-day Iraq, included monumental statues of winged bulls, bearded horsemen and other figures, all symbols of an ancient Mesopotamian empire in the cradle of Western civilization.

The discovery that extremists removed some statues before using heavy equipment to destroy much of the site Thursday was cold comfort as outrage spread over the extremists’ latest effort to erase history.

United Nations Secretary-General Ban Ki-Moon considers the destruction a war crime, his spokesman said in a statement.

Iraq’s most revered Shiite cleric, the Grand Ayatollah Ali al-Sistani, said in his Friday sermon that the extremists are savaging Iraq, “not only in the present but also to its history and ancient civilizations.”

“I’m shocked and speechless,” said Zeid Abdullah, who lives in nearby Mosul and studied at the city’s Fine Arts Institute until the extremists shut that down. “Only people with a criminal and barbaric mind can act this way and destroy an art masterpiece that is thousands of years old.”

A farmer from a nearby village said Friday that militants began carrying tablets and artifacts away from the site two days before the attack, which began Thursday afternoon. The militants told the villagers that the artifacts are idols forbidden by Islam and must be destroyed, the farmer said, speaking anonymously for fear of reprisals.

But the group also is known to have sold off looted antiquities as a source of revenue.

Some statues were “put on big trucks, and we don’t know where they are, possibly for illicit trafficking,” UNESCO Director General Irina Bokova said.

U.N. officials have seen images of destroyed Assyrian symbols including statues with the head of a man, the torso of a lion and wings of an eagle. These symbols were referred to in the Bible and other sacred texts, she said.

“All of this is an appalling and tragic act of human destruction,” she said.

U.N. officials were studying satellite imagery of the destruction, since it remains too dangerous to approach the site, she said.

These violent Sunni extremists have been campaigning to purge ancient relics they say promote idolatry that violates their interpretation of Islamic law. A video they released last week shows them smashing artifacts in the Mosul museum and in January, the group burned hundreds of books from the Mosul library and Mosul University, including many rare manuscripts.