FOR the first time in nearly two millennia, the northern Iraqi city of Mosul is without Christians, after a warning from Islamic State militants that they faced death if they did not convert to Islam or agree to pay a protection tax (jizya in Arabic).

A statement to this effect was read out from mosques after noon prayer on Friday, and Christians were given until midday on Saturday to decide on what to do. "We offer them three choices: Islam; the dhimma contract (for non-Muslims) involving payment of jizya; if they refuse this, they will have nothing but the sword," the Islamic State said.

All decided to leave. "Christian families are on their way to Dohuk and Irbil," in the neighbouring autonomous region of Kurdistan, the Chaldean Patriarch of Babylon and Archbishop of Baghdad, the Most Revd Louis Raphael Sako, told the AFP news agency on Saturday.

They crammed what possessions they could into cars and other vehicles, and fled for their lives. Islamists have also seized control of the fourth-century Syrian Catholic Mar Behnam monastery, close to Mosul, expelling the monks and not allowing them to take possessions with them.

Over preceding days, Islamist fighters had marked Christian houses in Mosul with the Arab letter N, standing for Nasrani (an Arabic word for Christian). Many social-media users have since been using the Arabic letter N as a profile picture in solidarity with the Christians of Iraq.

The Syrian Catholic Patriarch of Antioch and all the East of the Syrians, His Beatitude Ignace Joseph III Younan, told Vatican Radio that the Islamists in Mosul had burned to the ground the Syriac Bishop's office, residence, and library, destroying everything inside. "It's terrible," he said. "This is a disgrace for the whole international community." He said that the Christians in Iraq, Syria, and Lebanon "weren't imported; we've been here for millennia and, therefore, we have the right to be treated as human beings and citizens of these countries".

A report in The New York Times said that the Islamists removed the cross from St Ephrem's Syriac Orthodox Cathedral in Mosul, and raised a black flag in its place. It said that they also destroyed a statue of the Virgin Mary in the city.

Mosul's Christian community totalled about 60,000 before the US-led invasion of Iraq in 2003. Many Christians subsequently fled to Mosul from other parts of Iraq, believing it to be safe. But, by June this year, the number had dropped to 35,000, and fell sharply when the Islamic State took control. Some Christians had hoped that they could carry on living in the city, keeping a low profile. But last week's ultimatum made them think again.

The Islamic State's threat to Christians has been widely denounced. "Our brothers and sisters are persecuted; they are chased away," Pope Francis told pilgrims at the Vatican on Sunday. He assured Christians in Iraq and the Middle East as a whole of his constant prayers. "Violence isn't overcome with violence," he said. "Violence is conquered with peace."

The British Ambassador to Iraq, Simon Collis, tweeted on Monday that he had met Patriarch Sako "and shared our deep concern" about the persecution of Christians and others by the Islamic State in Mosul. The Islamist group, he said, "drove Mosul's Christians from a city they had prayed in for 1800 years. Churches were burned and houses marked with N."

The Bishop of Coventry, Dr Christopher Cocksworth, speaking on Tuesday, said: "The determined will of ISIS to evict Christians from Mosul and eradicate Christianity from the areas they seek to control is deeply distressing and terrifyingly cruel.

"It is incumbent on us all to speak out against such injustice and violence, to stand with Christians who are suffering in this way and, in so doing, also to stand with Shiite Muslims and other minority communities who are being persecuted in such terrifying ways. All people of responsible faith must stand together to protect each other: Muslim speaking for Christian, Christian speaking for Muslim."

A prayer vigil for Christians in Iraq is to be held outside the Houses of Parliament on Saturday, from 11.55 a.m. to 1 p.m.