Thousands of people have joined together on Twitter to express solidarity with persecuted Christians in Iraq, using the #WeAreN.

'N', or ن in Arabic, is the symbol used by the Islamic State (IS or ISIS) to identify who is a Nazarene - a Christian. It has been drawn on doorways and in front of houses in captured Iraqi cities, allowing militants to quickly assert where the loyalties of the inhabitants lie.

Last week, members of the extremist Sunni Muslim faction drove Christians out of the historic city of Mosul, where members of the faith have lived for the past 2,000 years. They were told to either flee the city, convert to Islam, or pay a tax for the right to be a Christian. Those who refused now risk death "by the sword".

"For the first time in the history of Iraq, Mosul is now empty of Christians," Patriarch Louis Sako told AFP following Friday's harrowing events.

"The heinous crime of the Islamic State was carried out not just against Christians, but against humanity," he added in a sermon in Baghdad on Sunday, which was attended by local Christians and around 200 Muslims - many of whom wore t-shirts branded with the words "We are N", "I am Iraqi, I am Christian", or simply "ن".

"This has never happened in Christian or Islamic history," Sako warned.

People all over the world are now joining in with the condemnation of IS, which - led by Abu Bakr al-Baghdadi - is attempting to found a pan-Islamic state across a stretch of northern Iraq and Syria.

The Church of England yesterday changed its Twitter photo to a 'We are N' symbol:

And it has been joined by others across the globe.

The Times yesterday published a letter by former bishop, Dr Geoffrey Rowell, in which he denounced the "savage attacks" on "ancient Christian communities" in the Middle East, labelling them "deeply troubling" and "chilling".

Referring to the storming of a fourth-century Syrian monastery by IS on Sunday, in an attack which forced the resident monks to flee, Rowell wrote: "The desecration of churches and tombs, the seizure of the ancient monastery and pilgrimage place of Mar Behnam, the human tragedies of refugee families dispossessed of their homes, are an unfolding tragedy in the latest martyrdom suffered by Christians".

As IS continues to gain momentum - and followers - fears are mounting that it will soon capture Iraq's capital Baghdad. Militants have claimed responsibility for a suicide bombing in the city last night, which killed 33 civilians and injured dozens more.

The explosion, which took place at the site of an important Sh'ite shrine in Kadhimiya, is the latest in a string of bombings in Baghdad, including several on Saturday which killed 27 people.