The Islamist militants controlling the Iraqi city of Mosul have ordered all remaining Christians to leave town immediately or face execution, according to news sources.

Middle East Concern, a London-based association of Christian-rights agencies with operations in the Middle East, reported Friday that the militants controlling Mosul had summoned Christian leaders to attend a July 17 meeting. At that meeting, the militants were to announce that Islamic rules would apply to non-Muslims, according to Middle East Concern., an Arabic-language website with a focus on Christian issues in the region, reported Friday  that the point of the meeting, called by the Islamic State in Iraq and the Levant, or ISIS, was to instruct Christians to either pay a tax to the Muslim leadership of the community, or convert to Islam.

ISIS has taken to identifying itself simply as the Islamic State.

The Christian leaders did not show up for the meeting. Shortly thereafter, vehicles passed through Mosul with loudspeakers, announcing that all Christians had until noon Friday to leave the city “or else face execution,” Middle East Concern reported.

“Most Christian families have now fled from Mosul, many to areas of Northern Iraq under Kurdish control,” according to Middle East Concern.

A World Watch Monitor source in Erbil, the capital of Kurdistan region, said a Christian family in Mosul reported by phone that explosions were heard overnight Thursday in Mosul. On Friday, as the family attempted to pass through a Mosul checkpoint, ISIS agents forced them out of their car and confiscated their belongings, put them in a separate vehicle, then drove them several minutes down the road, and ultimately forced them out to continue their journey on foot, according to the source.

World Watch Monitor is withholding  the source’s name to protect the source’s safety.