Islamic State is to convert one of the largest churches in Mosul into a mosque for its radical fighters.

The announcement was made in notices posted in the streets of the city, which fell to the militants a year ago. Formerly the heartland of Iraq's Christian population, there are now believed to be no Christians left in Mosul after they were forced to convert, flee or be killed.

The church threatened with conversion is the Syrian Orthodox Church of St Ephraim, according to Fides, the Vatican's news service. It was taken over by the militants a year ago and will be reopened as a "mosque of the mujahideen". According to local Iraqi media reports, the church has been draped with Islamic State's notorious black and white logo, with "There is no God but Allah" and "Prophet Mohammed" written on it.

The militants have also removed the cross from the church's dome and emptied the building of all its furniture and Christian symbols.

Nuri Kino, founder and president of A Demand For Action, a group advocating the protection of ethno-religious minorities such as Assyrians and Yazidis in the Middle East, told Newsweek that the move was proof of Islamic State's intentions regarding the Christian minority.

"A year ago they said 'Convert, pay or die' then it turned out to be a lie, that even if you pay you will not be able to stay," he said.

"If they changed a church to a mosque it is further proof of their cleansing, something that many call a genocide. They destroy our artefacts, our churches and try to erase us in any way they can."