Walkers are being asked to be on the lookout for a missing man who may be in the Deeside area.
It is thought Robin Green, 70, could be walking in the Glen Dye area south of Banchory.
He was reported missing from his home in Aberdeen and was last seen on Thursday in the city, but Police Scotland said he may have gone walking.
Inspector David Hoyle, who is leading the search, said: “It has been several hours now since Mr Green was reported missing to police and there are increasing concerns for his safety and welfare.
“There is a chance he may have slept outside overnight and I must ask the public to please keep an eye out for him, and to let us know if you see anyone, or have seen anyone, matching his description.
“Because of the terrain that needs to be searched we will be utilising the Police Scotland helicopter and mountain rescue support.
“I would appeal to dog walkers, walkers or simply anyone who lives in the local area to please keep a look out for Mr Green. Please check your gardens, outbuildings, and the surrounding area. Likewise if Mr Green could contact us directly to let us know he is safe and well I would urge him to do so.
“Anyone with information regarding the whereabouts of Mr Green, or any possible sightings of him, is asked to contact Police Scotland on 101.”
Mr Green, is described as 5ft 9ins (1.75m), of a slim build with long grey hair and beard. When last seen he was wearing a green wax jacket, a red jumper and dark dress trousers.