Closure-threatened Brechin Cathedral is being plagued by fire-raising vandals.
There are now fears the building could be put at further risk unless the vandalism can be “nipped in the bud”.
Shocking CCTV footage shows youngsters using the building as a playground. They can be seen ripping down church notices and setting fire to them in the porch.
Teenagers have also been caught running over pews, climbing up to the choir loft and drinking vodka, smoking in the church, walking along the ledges of the historic stained-glass windows in the chancel and entering the pulpit and using a hymn book as a frisbee.
Extra security measures are now being put in place at what is one of the oldest sites of worship in Scotland.
Archie Milne, church elder, said graffiti has also been scratched on a church wall and extra security measures are now being put in place in what is one of the oldest sites of worship in Scotland.
“The church is now closing an hour earlier to the public at 4pm,” he said.
“Extra locks have been put on doors inside the building and anti-climb paint will be put down on the gates and railings.
“It’s sad that we’re having to go to these lengths but we have to protect the building.
“We have nothing against youngsters coming in – the place is open for everyone and anyone as long as they respect it.
“But this behaviour is not acceptable and it seems to be every four or five years that this kind of event occurs.
“I don’t believe this is malicious pre-planned behaviour but it’s just the way society is.
“The kids are bored but our fear is what happens next if this is allowed to continue?”
Session clerk Douglas Taylor said they first noticed something was wrong when they found a door open inside the church. The door can only be accessed from a secure area which is when they discovered the teenagers were pulling themselves up into the choir loft.
“It’s very disrespectful behaviour and it’s got to stop before there is a serious incident,” he said.
“We’ve had problems over the past three weeks with the youths.
“In one incident they ripped down notices from our notice board in the porch and set fire to them after the gates had been locked.
“They also got into the pulpit and were throwing a copy of a hymn book between each other like a frisbee.
“There have been several other incidents which have been caught on CCTV and copied on a disc and handed to the police.
“We have visitors who travel from all over the world to visit the church and this type of behaviour doesn’t give them a good impression of Brechin.”
Brechin owes its origins to the medieval cathedral, which is the oldest building in the burgh, and the Celtic monastery which preceded it.
The building itself is to celebrate its 800th anniversary in 2020 and the oldest part of the cathedral is the Pictish round tower which is about 1,000 years old.
A spokeswoman for Police Scotland said: “We are aware of the issues and officers will be carrying out extra patrols in the area.
“Anti-social behaviour will not be tolerated.
“It is upsetting for the local community that vandals are damaging private property.
“If you witness this kind of behaviour, please contact Police Scotland on 101.”