The northern city of Mosul – where the Christian community once numbered 60,000 – has been virtually emptied of Christians following threats from the Islamic State of Iraq and Syria, formerly known as ISIS. Islamic State militants warned that Christians should convert to Islam, pay a special tax or face death.

Before the deadline passed, militants marked Christian homes with the Arabic letter ‘n’ for ‘Nasarene’, meaning ‘Christian’, while Shi’ite homes were marked with an ‘r’ for ‘rejecter’. Globally, many Christians have amended their profile pictures on social media to show the Nasrani symbol as a sign of solidarity.

An impassioned letter from Louis Sako, head of the Chaldean Catholic Church, said: ‘Should this direction continue to be pursued, Iraq will come face to face with human, civil and historic catastrophe.’

The actions of the Islamic State have been condemned around the world by figures including the UN secretary general, Ban Ki-moon, Pope Francis and general secretary of the World Council of Churches, Rev Dr Olav Fykse Tveit.

Around 10,000 Christians fled Mosul before the offensive, leaving an estimated 25,000 behind. The majority of those remaining have since left, many of whom travelled on foot, taking only what they could carry. Many were reportedly robbed at checkpoints.

Islamic State militia have allegedly burned an ancient church and destroyed what Shi’ite Muslims believe to be the tomb of Jonah.