London : The archaeologists who are assessing the damage caused by Islamic State (IS) terrorists to the tomb of the prophet of Jonah have found a palace which dates back to 600BC, a media report said.

The previously untouched palace buried under the ruins of the Nebi Yunus shrine containing what Muslims and Christians believe to be the tomb of Jonah -- was destroyed by IS terrorist in July 2014.

The shrine is located on top of a hill in eastern Mosul, a city in northern Iraq was retaken from IS control by Iraqi army forces last month.

According to The Telegraph, IS terrorists dug tunnels deep under the shrine. These tunnels were not professionally built, leaving them unstable and at risk of collapse within the next few weeks, burying the ancient palace.

"We fear it could all collapse at any time. There are cave-ins in the tunnels every day," archaeologist Layla Salih, was quoted as saying.

The palace was renovated and expanded by King Esarhaddon after it was built for his father Sennacherib.