Baghdad - The battle for Iraq's second city Mosul neared the remains of ancient Nimrud on Thursday, the military said, raising fears for the famed heritage site already ravaged by jihadist bombs and sledgehammers.

Troops and allied militia were advancing on two villages held by the Islamic State group near the ancient site some 30km south of Mosul, the Joint Operations Command said.

"Units of the 9th Armoured Division and the Hashed al-Ashaeri (tribal militia) are beginning to advance to liberate the villages of Abbas Rajab and Al-Nomaniyah, toward Nimrud," it said, later announcing that Abbas Rajab had been retaken.

Nimrud was the one of the great centres of the ancient Middle East. Founded in the 13th Century BC, it became the capital of the Assyrian empire, whose rulers built vast palaces and monuments that have drawn archaeologists from around the world for more than 150 years.

Many of its monumental stone sculptures and reliefs were taken away for display in museums around the world but some of the more massive structures remained in place when the jihadists swept through in mid-2014.

In April last year, ISIS posted video on the internet of its fighters sledgehammering monuments before planting explosives around the site and blowing it up.

It was part of a campaign of destruction by the jihadists against heritage sites under their control that also took in ancient Nineveh on the outskirts of Mosul, Hatra in the desert to the south and Palmyra in neighbouring Syria.

ISIS says the ancient monuments are idols that violate the teachings of its extreme form of Sunni Islam.

Ancient Nineveh

But that has not stopped the group from trafficking artefacts it purports to revile on the black market to fund its operations.

It is unclear what still remains of Nimrud's ancient ruins as Iraqi forces move closer.

But it is just one of a number of treasured heritage sites that are threatened with further damage by the offensive that the government launched on October 17 to retake Mosul, the jihadists' last major stronghold in Iraq.

The area where ancient Hatra is located may see fighting between ISIS and pro-government militias who aim to retake the town of Tal Afar, which commands Mosul's western approaches.

Ancient Nineveh is also in the path of advancing troops.