Christian nuns living in Iraq have described barbaric atrocities committed by Islamic State militants.

In a letter published by RNS, the Dominican Sisters of St Catherine of Siena write of a time of "displacement, of humiliation, of exile" since leaving their historic home in the Nineveh Plain more than two years ago when ISIS captured the traditionally Christian area.

As Iraqi and other troops continue their advance on Mosul, Christian soldiers fighting to defeat ISIS have been sending pictures of churches and graveyards to the nuns.

The nuns say they are grateful their towns and buildings are being recaptured, but they are shocked by what the pictures reveal.

"They are showing our churches, homes, schools, and convents, hospitals burned and destroyed after they had been looted.

"We were shocked that our cemeteries were dug: Is it possible that even the dead did not survive their cruelty!"

They fear that even when ISIS is driven out, they will not be able to return for some time because so many buildings have been mined.

They are also worried also about who will administer the area when the Christians do eventually return. Chaldean church leaders have already requested arrangements for a Christian-led administration in the Nineveh area but so far there is no sign the Iraqi government will accede to this.

The sisters go on in their letter to describe the narrow escape from ISIS fighters by seven students living in one of four houses attached to their convent.

The escape, reported by Christian Today last week, is also described in detail by the Dominican Sisters of Hope who document how the seven young women woke to find heavily armed men wearing explosive belts climbing the walls and in the gardens.

"For the day, four terroists were in the same house as seven students. The terrorists were in an adjacent room, eating and drinking while the girls hid under their beds. The terrorists eventually blew themselves up inside the house on Saturday morning. Amazingly, the seven students remained totally still under the beds for eighteen hours. The terrorists had no idea that they were there."

They were saved when Iraqi soldiers recaptured the house.

The Dominican Archbishop Yousif Toma wrote in a statement: "I have to say I was amazed by the courage of the girls and they obeyed the instructions with great accuracy... We must not forget the role played by the security forces of the efficiency and professionalism in keeping the terrorists confined."