Turkish authorities have cancelled an annual service at the historic Panagia Sumela monastery near the Black Sea town of Trabzon, raising fears among Orthodox believers that it may be permanently banned.

The monastery is built into a rock face 1,200 metres high and was founded in AD 386 in the reign of the Byzantine Emperor Theodosius. It was abandoned in 1923 after forced population exchanges between Greece and Turkey led to the evacuation of the city's Christian population and became derelict. However, annual services resumed in 2010 and a restoration programme began.

The monastery was closed for a year last September for renovation work in order for it to qualify as a UNESCO World Heritage Site. Ecumenical Patriarch Bartholomew, who was to lead the service, has been told the works mean the August 15 service cannot take place.

However, according to the Pappas Post news service, sources within the Patriarchate of Constantinople believe the ban may become permanent and that Christian worship may never take place in the monastery again.

The annual service has seen hundreds of Greeks, many of them descendants of those who lived in the region before the 'exchange of populations', return as pilgrims.

Fears that the ban will be permanent come amid increasing pressure on Turkey's Christians following the attempted military coup against the regime of President Recep Tayyip Erdogan. Some Turkish media outlets have suggested that Patriarch Bartholomew was complicit in the coup.