The operation to retake the Iraqi city of Mosul from Islamic State risks more serious damage to heritage sites, according to observers on the ground.

The museum in Mosul was vandalised after IS overran the city in 2014 and many priceless artefacts were lost. Other ancient cities including the World Heritage Sites of Hatra and Nimrud were attacked, with ancient monuments and statues destroyed with sledgehammers and explosives.

Local officials say IS has fighters deployed at or near historic sites.

Ahmed al-Assadi, the spokesman for the Hashed al-Shaabi, an umbrella organisation for pro-government paramilitary forces, told AFP: "Our information indicates that [IS] has a presence in the archaeological sites."

He added: "We expect [IS] will try to lure the advancing forces to the sites for the purpose of increasing their destruction."

Assadi said Hashed would use "extreme care" near the sites and that "every effort must be made to protect and preserve them".

When the operation to retake Mosul was launched on October 17, the head of UNESCO urged parties to the conflict to protect heritage sites.

"I call on all involved in military action to protect cultural heritage and refrain from any military use or targeting of cultural sites and monuments," Irina Bokova said.

The coordinates of heritage sites have been passed to the Iraqi military in an effort to limit airstrikes in sensitives areas.

UNESCO has said of the IS vandalism: "The demolition of the Mosul museum and the destruction of archeological remains in Nineveh will remain in human history as one of the most barbaric attacks against the heritage of humanity.

"These crimes must not remain unpunished."