The al-Qaeda offshoot ISIS or Islamic State (IS) told Christians they must either convert to Islam, pay a religious levy, leave or face death. The ultimatum to Mosul's Christian community was read out after Friday prayers and has a deadline of mid day local time (09.00 UTC) Saturday.

Many of the city's Christians had already fled as IS fighters took over large areas of north and western Iraq and declared an Islamic state or caliphate. Iraqi security forces have begun an advance into the north, to try to recapture areas lost to the militants.

Ten years ago there were 100,000 Christians living in Mosul. But attacks on Christians since the 2003 US-led invasion of the country saw those numbers fall to about 25,000. There are no accurate figures for the number of Christians who fled to Kurdistan in advance of the IS takeover of the city last month, or how many were still in the city on Saturday.

The ultimatum given to the Christian community was based on an ancient "dhimma" contract under which non-Muslims were protected in Muslim lands in return for a levy known as "jizya."

The ISIS leader Abu Bakr al-Baghdadi or Caliph Ibrahim as he is now known, had set the deadline for Christians who did not want to stay and live under those terms to "leave the borders of the Islamic Caliphate."

His statement warned: "After this date, there is nothing between us and them but the sword."

jm/av (Reuters, AFP)