Islamic State militants have looted and bulldozed the ancient Assyrian city of Nimrud in northern Iraq, it has been confirmed.

"ISIS continues to defy the will of the world and the feelings of humanity. They violated the ancient city of Nimrud and bulldozed its ancient ruins," Iraq's Ministry of Tourism and Antiquities said in a statement.

The government did not elaborate on the extent of the damage, but said heavy machinery was used and "archaeological attractions dating back 13 centuries BC" were taken.

"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," a tribal source from the area told Reuters.

"There used to be statues and walls as well as a castle that Islamic State has destroyed completely."

"We are very saddened and devastated by the continued destruction to our heritage," a spokesperson for campaign group A Demand For Action told Christian Today.

"Why is the international community not helping to preserve these ancients sites?"

Axel Plathe, director of the UNESCO Office for Iraq, called it "another appaling attack on Iraq's heritage".

Iraqi archaeologist Dr Lamia al-Gailani told the BBC that Islamic State is "erasing our history".

"I wish it was a nightmare and I could wake up. I can't understand their reasons," she said.

Nimrud was considered one of the most important cities in the Assyrian empire. Located south of Mosul, which was overrun by IS militants last June, it was established as the capital by Assyrian king Ashurnasirpal II who reigned between 883 and 859 BC. Many of the carvings from his palace in the city are now on display at the British Museum in London.

The destruction at Nimrud came a week after Islamic State released a video showing them destroying Assyrian era statues and sculptures in Mosul.

The group has specifically targeted Christian sites, and experts claim militants have looted and sold on millions of pounds worth of artefacts from ancient churches across Iraq and Syria to fund their regime.

A fourth-century Syrian monastery was seized by insurgents last July, and militants also destroyed a tomb believed to be that of biblical prophet Jonah.

More recently, over 200 Assyrian Christians were abducted by ISIS near Tel Hmar, south of the Khabour river in Syria. 24 people are thought to have bene released so far after paying a tax for being non-Muslim.

Additional reporting by Reuters