York's city walls and St Olave's church have been vandalised with red painted hieroglyphics.
Concerns have been raised that it could be a hate crime, as the graffiti on both the church doorway and bridge include 88 - a well-known code for Heil Hitler among far right groups.
The Diocese of York has issued a statement on behalf of the church expressing their disappointment with the vandalism.
A spokesman for the Diocese of York said: "The graffiti on St Olave's church door and on the medieval York city walls is upsetting for everyone who loves the city's historic buildings.
"St Olave's has taken advice from expert advisers and from the Diocese of York, and has arranged the careful removal of the paint from the door.
"The church is co-operating with a police investigation and so is unable to comment any further."
The 13th century church, St Olave's Church was dedicated to the patron saint of Norway, St Olaf, in 1055.
After the Norman Conquest of 1066, the church of St Olave's became part of the Benedictine order in York. It now describes itself as part of the liberal Catholic tradition of the Church of England.