The UN's cultural agency called for emergency measures on Thursday to prevent further looting at the historic Iraqi city of Nimrud which has been wrecked by Islamic State militants.

Nimrud, founded in the 13th century BC on the Tigris river about 30 kilometres (18 miles) southeast of Mosul, was retaken by Iraqi forces on November 13 after it was overrrun by IS in 2014.

Journalists who visited immediately afterwards found shattered statues, wrecked ancient palaces and bulldozed structures in one of the region's most important archaeological sites.

A fact-finding mission sent by the UNESCO agency this week confirmed "large-scale, systematic" destruction and recommended greater protection for what remains of the site.

"Emergency measures will entail the immediate physical protection of the site in order to allow for detailed documentation and preventing potential looting of remaining fragments," said a statement.

UNESCO, which works to safeguard world heritage and culture, will liaise with Iraqi authorities to help document and then rebuild the site which it called "important for the history of humanity."

A conference to discuss reconstruction will take place on February 27 in Paris.

The Islamic State group has carried out a campaign of "cultural cleansing" in territory under its control in Iraq and Syria, razing many ancient relics and looting others to sell on the black market.

In April 2015, the group released a video of its fighters destroying monuments in Nimrud before planting explosives around a site and blowing it up.

In the video, militants with sledgehammers and power tools broke artefacts before rigging the site with large barrels of what appeared to be explosives.