Baghdad - Islamic State of Iraq and the Levant (ISIL) fighters have used a bulldozer to start destroying a 3,000-year-old Assyrian city near Mosul in Iraq, archaeologists and other sources have told Al Jazeera.

The demolition at Nimrud on Thursday comes less than a week after video was released showing ISIL fighters destroying ancient artefacts in a Mosul museum.

"They came at midday with a bulldozer and started destroying the palace," said an Iraqi official in touch with antiquities staff in Mosul.

She said the winged-bull statues known as lamassu at the gates of the palace of Ashurnasirpal II had been smashed. It was not clear what else had been destroyed on the site, about 20km southeast of Mosul.

In last week's ISIL video , fighters were shown using power drills and sledgehammers to try to destroy similar statues at the ancient site of Nineveh, within Mosul.

The mutli-tonne figures were placed at the palaces' gates as protective spirits.

One source told Al Jazeera the fighters warned Mosul residents last week that they would move on to Nimrud next. Hatra, a World Heritage Site, is also believed to be in danger.

Since 2002, the World Monuments Fund has listed Nimrud as one of the world’s most endangered sites. The intricate stone reliefs, exposed to the elements, have been decaying. Without security around the site, it has been exposed to looters.

The palace belonged to King Ashurnasirpal II, who ruled a powerful empire that included Iraq, the Levant, lower Egypt and parts of Turkey and the Levant. The palace was built with precious wood, marble and other materials brought from the furthest reaches of his kingdom.

Nimrud, known as biblical Calah, is believed to have first been settled 7,000 years ago. At its height, up to 60,000 people lived in the walled city, which contained lush gardens and sprawling parks.

Mostly excavated by the British, with the finds taken to the British Museum, the most spectacular discovery was an Iraqi one.

In the late 1980s Iraqi archaeologist Muzahim Mahmood discovered a royal tomb containing one of the biggest finds of the last century - hundreds of pieces of golden jewelry and other objects belonging to an Assyrian queen.

Iraq's Ministry of Tourism and Antiquities on Thursday condemned the destruction at Nimrud, stating that ISIL "continues to defy the will of world".