Police are investigating a series of bizarre incidents in which more than 25 horses on a farm have had their tails and manes cut.

No horses have been hurt, as was the case in a series of similar incidents four years ago which were thought to have been linked to the occult.

There have been at least 12 separate incidents, all at Balhagerty Farm near Laurencekirk in Aberdeenshire, and some of the horses have been targeted several times.

They began in January and have all taken place during the hours of darkness in fields and stables at the farm.

The most recent incident was sometime between midnight on Sunday, March 11 and the following morning. In 2003, also in the Laurencekirk area, there were a number of attacks on horses including stabbings, sexual abuse and assault, while others had their tails chopped off or manes plaited or covered in a sticky substance.

Horse owners also reported finding ritualistic symbols hidden in corners of fields, ranging from tiny stone altars to pre-Christian power signs such as double-headed axes.

However, in the latest series of incidents the horses have not been injured.

"There is nothing to suggest this is linked to the occult but I have to keep an open mind," said Sergeant Kenny McGeough, who is leading the investigation.

He said he had been unable to identify any motive.

"The horses are all from one farm but we don't know if it is personal," he said. "The owners cannot think of any reason. I am keeping an open mind but it is bizarre.

"The family have had no threats and, while they seem to be targeted, for what reason we do not know. The commercial value of the tails is negligible so that seems unlikely.

"There have been a disturbing number of attacks to the horses on the farm and although no animal has been physically injured, I am extremely concerned that the attacks will continue and escalate in violence."

He appealed for anyone who could help to contact the force, adding: "If I could find the motive that would be a massive step forward."

Gail Sefton, of East Balhagerty Farm, said they had been there for 18 years and had never experienced anything like this.

"It is very distressing. We have all been spending a lot of late nights patrolling to prevent the attacks.

"Whoever is doing it obviously knows about horses and is enticing them with something tasty. They have been doing a lot of licking the day after the attacks as if they are expecting something tasty."

She said they were mainly breeding horses but some of the youngsters had had manes and tails cuts so if someone wanted to buy them to show it would affect their value.

She said it would take more than a year for the hair to grow back and the horses would be unable to flick flies away with their tails in the summer.