Some of the damaged gravestones date back to the 19th Century
Vandals have damaged part of a 12th Century Northamptonshire abbey.
Northamptonshire Police have appealed for help in tracking down those responsible for smashing gravestones in Delapre Abbey's pet cemetery.
A police spokesman said coping stones were also removed from an 18th Century Grade II listed wall.
The Friends of Delapre Abbey, a group of volunteers which maintains the building in London Road, Northampton, said they were "very angry".
Graham Walker, the group's chairman, said: "I just hope that somebody out there knows something about who has done this."
Sandstone coping stones were removed from the top of the damaged wall before being smashed on the floor.
The damage was discovered on Saturday morning
"They must have had some sort of tool to lever them off," Mr Walker said.
He added: "To break the largest gravestone in the pet cemetery they would have to have had a sledgehammer because it's reinforced concrete.
"They've broken it into small pieces.
"Everybody is very angry."
Delapre Abbey dates back to 1145.
It was built by the son of Simon de Senlis, the second Earl of Northampton and is now owned by Northampton Borough Council.