Officials in Iraq say Islamic State militants have begun destroying the ancient Assyrian city of Nimrud. File footage shows the city, which was founded in the 13th century B.C. (Reuters)

Islamic State jihadists have bulldozed and looted the world-famous Nimrud archaeological site in northern Iraq in an act described Friday as a “war crime” by the United Nation’s cultural agency.

The destruction at the more than 3,000-year-old landmark — considered one of the most important archaeological sites uncovered in the past century — marked another blow against the area’s renowned pre-Islamic cultural heritage.

A statement late Thursday from Iraq’s Ministry of Tourism and Antiquities said the Islamic State continues to “defy the will of the world and the feelings of humanity” with this latest attack, in which the extremists used heavy military vehicles to crush treasured relics from one of ancient Mesopotamia’s greatest cities.

In Paris, UNESCO Director General Irina Bokova said the ravage of Nimrud amounts to a “war crime,” and she notified the prosecutor of the International Criminal Court.

Nimrud is considered a world heritage site by the United Nations Educational, Scientific and Cultural Organization, and many of its most prized artifacts were moved long ago to various museums.

File photo - Iraqi workers cleaning a statue of winged bull at an archeological site in Nimrud, southeast of Mosul. (Karim Sahib/AFP/Getty Images)

The second capital of the ancient kingdom of Assyria, Nimrud was built about 1250 B.C. and destroyed in 612 B.C. At its height, it was the center of one of the most powerful states at the time, reaching through modern-day Egypt, Turkey and Iran.

Nimrud is just south of Iraq’s largest city in the north, Mosul, which was captured by Islamic State militants last June.

Iraqi forces, aided by militia units, have launched an attempt to reclaim Tikrit — about 120 miles south of Mosul — as part of an offensive to push north into areas held by the Islamic State, which holds territory in Iraq and Syria.

Last week, a video was released showing apparent Islamic State militants destroying ancient statues and other artifacts at Mosul’s museum. The Mosul attack also was described by the United Nations as a war crime.

[Watch: Video of Mosul museum destruction]

Art collectors in London have also reported seeing looted items from Islamic State-controlled areas appearing in the British capital.

The discoveries at Nimrud have been described as among the most significant archaeological finds of ancient Mesopotamia. The area was known by Western experts for centuries, but extensive excavations began after World War II.

Nimrud also showcases the region’s rich history as an important crossroads among pre-Islamic civilizations, including areas mentioned in the Bible and other texts.

The Islamic State claims that the area’s pre-Islamic heritage of ancient shrines and statues represents past idol worship that it views as heretical.

A tribal source from nearby Mosul confirmed to the Reuters news agency that the Islamic State had pillaged the site, on the banks of the Tigris River.

“Islamic State members came to the Nimrud archaeological city and looted the valuables in it, and then they proceeded to level the site to the ground,” the source told Reuters.

“There used to be statues and walls as well as a castle that Islamic State has destroyed completely,” the source said.

“Daesh terrorist gangs continue to defy the will of the world and the feelings of humanity,” Iraq’s Ministry of Tourism and Antiquities said, referring to the Islamic State by the name widely used in Arabic.

“In a new crime in their series of reckless offenses, they assaulted the ancient city of Nimrud and bulldozed it with heavy machinery, appropriating the archaeological attractions dating back 13 centuries BC,” it said.

In a message posted on Twitter, the former prime minister of Iraq’s semiautonomous Kurdish region, Barham Salih, called the Nimrud destruction “slaughtering the present and erasing humanity’s heritage.”

Many of Nimrud’s most famous surviving monuments were removed years ago by archaeologists, including colossal Winged Bulls, now housed in London’s British Museum. Hundreds of precious stones and pieces of gold were moved to Baghdad.

Ruins of the ancient city remain at the northern Iraqi site, however, which has been excavated by a series of experts since the 19th century. British archaeologist Max Mallowan and his wife, crime writer Agatha Christie, worked at Nimrud in the 1950s.

After the U.S.-led invasion of Iraq in 2003, looters pillaged many archaeological sites and museums across the country, but Nimrud was largely spared.

The destruction hearkens back to Taliban rule in Afghanistan, when other famous pre-Islamic sites were targeted, including the demolition of two giant 1,400-year-old Buddha statues.

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