The Islamic State group, in its bid to do away with all monuments and heritage sites that don't line up with its religious beliefs, has levelled the oldest Christian monastery, St Elijah's, in Mosul, Iraq, according to Associated Press (AP), which possesses visual confirmation.

The 1,400-year-old monastery had been used as a place of worship when American troops were in Iraq. It was a brick-and-mortar building and had the Greek letters chi and rho, the first letters in the name of Christ, on its gate. Images prior to the destruction showed the 27,000-sq-foot structure did not have a roof and stood in a state of partial repair. It also had 26 rooms. However, the most recent images show the monument has been turned into grey-white powder.

"I can't describe my sadness," Reverend Paul Thabit Habib told AP from Irbil, Iraq. "Our Christian history in Mosul is being barbarically levelled. We see it as an attempt to expel us from Iraq, eliminating and finishing our existence in this land.

"Oh no way, it's just razed completely," said Suzanne Bott, who had worked on restoring the monastery as a US State Department cultural advisor in Iraq, after seeing the images. "What we lose is a very tangible reminder of the roots of a religion," she told AP.

Satellite imagery firm DigitalGlobe had aimed a high-resolution camera at the site of St Elijah's monastery in Iraq, at the behest of AP, and the images they received confirmed fears that the centuries-old Christian monastery had been flattened.

"Bulldozers, heavy equipment, sledgehammers, possibly explosives turned those stone walls into this field of gray-white dust. They destroyed it completely," Stephen Wood, CEO of Allsource Analysis, said. "There's nothing to rebuild."

Wood, an image analyst, pegged the date of destruction of the monastery between 27 August and 28 September, 2014. 

With the destruction of St Elijah's monastery, Isis has added another heritage site of religious and historical value to the list of monuments it has razed in Iraq and Syria, where it commands territory. The group has destroyed mosques, tombs, churches and other places of worship such as the Arch of Triumph in the 2,000-year-old city of Palmyra, and the city of Apamea.