Every Sunday, behind thick basalt walls, the last members of a dying community gather to pray. They perform the liturgy in Aramaic, the language spoken by Jesus.

The pink marble pillars of the altar are remnants of the pagan sun temple that stood there before the people of Mesopotamia converted to Christianity. The bodies of priests are entombed in the walls, among them the bones of Doubting Thomas, it is said.

Until the 1960s there were several hundred followers of Assyrian Orthodoxy in Diyarbakir, a city in the southeast of Turkey that is now the de facto capital of the country's Kurds. Today there are only four families left, two of them living inside the compound of the Virgin Mary Church in the ancient walled district of Sur.

"They left for different reasons -- economic pressure, political pressure," said Saliba Acis, 43, who shows visitors around the church and lives there with his family. "Some went to Istanbul, others to America, Australia or Europe. Our population around the world is high, but the numbers who can come to the church are low."

The flight of Christians is not unusual in these parts. Assyrian communities in Iraq and Syria have been decimated since the rise of ISIS, with many of those who fled unlikely to return even though the "caliphate" has been crushed. But the congregation at the Virgin Mary are caught in the crossfire of a different war: President Recep Tayyip Erdogan's crackdown on Kurdish militants and the Turkish state's subsequent destruction of living history.

In 2015 the maze of impoverished streets surrounding the church became the scene of pitched battles between youth fighters aligned with the PKK, a Kurdish separatist militia, and the Turkish security forces. Civilians were evacuated from almost all of Sur, and the battle raged for three months. When it was over, much of the district lay in ruins.

Half of Sur is still behind barricades, off limits to locals as it undergoes reconstruction. The other half, where the Virgin Mary sits, is open but it too is set for complete redevelopment. The church and Sur's myriad ancient monuments will remain but everything around them will be razed, to be replaced with apartments. It is unlikely that the old Sur residents will be able to afford to live there. "The new houses are not for them, they are for richer people," said Cemal ­Ozdemir, the mayor of Sur and a member of the HDP, the main Kurdish party. "There are 35,000 people displaced from Sur. Some are living in other districts of ­Diyarbakir, some have moved to other cities. They were forced to sell their houses to the state."

Mr Ozdemir is not allowed into the closed area; it is under central government control. The same will happen to the neighbourhoods around the Virgin Mary once its turn for redevelopment comes. Not even UNESCO, which added the 3000-year-old city walls to its list in July 2015, before the fighting began, can halt the destruction. In its latest report it notes that it still has not been allowed into the area to assess the damage.

In August, 1400km away in Istanbul, Mr Erdogan laid the foundation stone on an Assyrian church in the Yesilkoy district. He said that it would add "richness" to the city and used the occasion to take a swipe at terrorism; a veiled reference to the Kurdish militants who fought the street battles in Sur.

"The real target of terror groups is our common homeland and the best way to disappoint them is to see our differences as our most important richness," he said.

But in Diyarbakir, under the ­ancient domed ceiling of the Virgin Mary, the congregation say they have little to thank the President for. "We get no support from the state," Mr Acis said. "This church is alive thanks to the community."