(AFP) -- The Islamic State group on Saturday released a video that shows militants smashing artefacts at the ancient Assyrian city of Nimrud in northern Iraq before blowing up the site. The undated video suggests that the site, on the Tigris river about 30km (18 miles) south-east of Mosul, was completely levelled. Destruction at the site was reported more than a month ago but the extent of the damage was unclear at the time. "Whenever we are able in a piece of land to remove the signs of idolatry and spread monotheism, we will do it," one militant said at the end of the video. Militants can be seen rigging large barrels filled with powder in a room whose walls are lined with imposing gypsum slabs, beautifully carved with representations of Assyrian deities. The ensuing footage shows a massive explosion that sends a mushroom of brown dust into the sky. Earlier, Isis militants are seen hacking away at the relief and statues with sledgehammers. One is shown sitting on the slabs and carving them up with an angle grinder. "God has honoured us in the state of Islam by removing and destroying everything that was held to be equal to him and worshipped without him," one militant says, speaking to camera.

In the jihadists' extreme interpretation of Islam -- statues, idols and shrines amount to recognising objects of worship other than God and must be destroyed. The ruins of the city founded in the 13th century BC were one of the most famous archaeological sites in a country often described as the cradle of civilisation. Nimrud, which is on UNESCO's tentative list of world heritage sites, is the later Arab name given to a settlement which was originally called Kalhu. The ancient city was first described in 1820 and plundered by Western explorers and officials over subsequent decades. It was also looted and damaged during the 2003 US-led invasion of Iraq.