Motorcyclists whose illegal activities terrorise forest walkers have been warned they will be prosecuted with the full force of the law.
Police in the north east have promised a crack-down on the anti-social behaviour that has also endangered horse riders.
Forestry staff say recklessly-driven bikes, whose owners have illicitly gained access to otherwise peaceful woodland and forest trails, could endanger lives.
Their behaviour has injured several riders and animals in recent months after horses were spooked and their riders thrown-off in panic.
In one incident the animal was also hurt after it ran into nearby traffic.
Neil Taylor, a recreation ranger with Forest Enterprise Scotland, said: “Lots of people use our forests expecting a quiet, traffic-free area.
“But we have had quite serious incidents where horses have been scared and people have been hurt.
“They are not terribly common but they do keep happening on an on-going basis and we know we have quite a lot of illegal activity near Aberdeen and up on the Moray coast.”
Sergeant Mark Conner said: “Not only is it illegal for unauthorised motor vehicles to access these forests but some of the people who do so are driving recklessly at speed across terrain that is more than likely not appropriate for this type of activity.
“This type of behaviour is not only putting themselves at risk of serious or fatal injury but also other members of the public who are enjoying our forests.”
Members of the public who witness such illegal activity are encouraged to report what they see by calling police 101.
They are asked to note as much detail as possible, including location, registration and colour of motorcycle and details of riders’ clothing.