Mosul, Iraq (AFP) -- When Islamic State extremists bulldozed the ancient monumental Mashki Gate in the Iraqi city of Mosul in 2016, it was part of the group's systematic destruction of cultural heritage.

Now, U.S. and Iraqi archaeologists working to reconstruct the site have unearthed extraordinary 2,700-year-old rock carvings among the ruins.

They include eight finely made marble bas-relief carvings depicting war scenes from the rule of the Assyrian kings in the ancient city of Nineveh, a local Iraqi official said Wednesday.

Discovered last week, the detailed carvings show a soldier drawing back a bow in preparation to fire an arrow, as well as finely chiseled vine leaves and palms.

The gray stone carvings date to the rule of King Sennacherib, in power from 705 to 681 BC, according to a statement from the Iraqi Council of Antiquities and Heritage.

Sennacherib was responsible for expanding Nineveh as the Assyrians' imperial capital and largest city -- siting on a major crossroads between the Mediterranean and the Iranian plateau -- including constructing a magnificent palace.

Fadel Mohammed Khodr, head of the Iraqi archaeological team working to restore the site, said the carvings were likely taken from Sennacherib's palace and used as construction material for the gate.

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"We believe that these carvings were moved from the palace of Sennacherib and reused by the grandson of the king to renovate the gate of Mashki and to enlarge the guard room," Khodr said.

Iconic

When they were used in the gate, the area of the carvings poking out above ground was erased.

"Only the part buried underground has retained its carvings," Khodr added.

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ALIPH, the Swiss-based International Alliance for the Protection of Heritage in Conflict Areas, said the Mashki Gate had been an "exceptional building."

IS targeted the fortified gate, which had been restored in the 1970s, because it was an "iconic part of Mosul's skyline, a symbol of the city's long history," it added.

ALIPH is supporting the reconstruction of the Mashki Gate by a team of archaeologists from Iraq's Mosul University alongside U.S. experts from the University of Pennsylvania.

The restoration project, which is being carried out in collaboration with Iraqi antiquities authorities, aims to turn the damaged monument into an educational center on Nineveh's history.

Related: Brief History of Assyrians

Iraq was the birthplace of some of the world's earliest cities.

It was also home to Sumerians and Babylonians and among humankind's first examples of writing.

But in the past decades, Iraq has been the target of artifacts smuggling. Looters decimated the country's ancient past, including after the 2003 U.S.-led invasion.

Then, from 2014 and 2017, Islamic State demolished pre-Islamic treasures with bulldozers, pickaxes and explosives. They also used smuggling to finance their operations.

Iraqi forces supported by an international coalition recaptured Mosul, the extremists' former bastion, in 2017.