BAGHDAD (AFP) - The Islamic State in Iraq and Syria (ISIS) group began bulldozing the ancient Assyrian city of Nimrud in Iraq on Thursday, the government said, in the militants' latest attack on the country's historical heritage.

ISIS "assaulted the historic city of Nimrud and bulldozed it with heavy vehicles," the tourism and antiquities ministry said on an official Facebook page.

An Iraqi antiquities official confirmed the news, saying the destruction began after noon prayers on Thursday and that trucks that may have been used to haul away artefacts had also been spotted at the site.

"Until now, we do not know to what extent it was destroyed," the official said on condition of anonymity.

Nimrud, which was founded in the 13th century BC, lies on the Tigris around 30km south-east of Mosul, Iraq's second city and the main hub of ISIS in the country.

The destruction at Nimrud, one of the jewels of the Assyrian era, came a week after the Islamist group released a video showing militants armed with sledgehammers and jackhammers smashing priceless ancient artefacts at the Mosul museum.

That attack sparked widespread consternation and alarm, with some archaeologists and heritage experts comparing it to the 2001 demolition of the Bamiyan Buddhas in Afghanistan by the Taleban.

In the militants' extreme interpretation of Islam, statues, idols and shrines are a corruption of the purity of the early Muslim faith and amount to recognising other objects of worship than God.

The group spearheaded a sweeping offensive last June that overran Nineveh province, where Mosul and Nimrud are located, and swept through much of Iraq's Sunni Arab heartland.

Iraqi security forces and allied fighters are battling to regain ground from the militants with backing from an international anti-ISIS coalition as well as neighbouring Iran.

But major operations to drive ISIS out of Nineveh are likely months away, leaving the province's irreplaceable historical sites at the mercy of militants who have no regard for Iraq's past.