The derelict remains of Scotland's first sanatorium have been destroyed in a deliberate blaze.

The Grade A-listed former Glen O'Dee Hospital in Banchory was gutted by the fire, which broke out shortly before midnight on Thursday.

A total of 62 firefighters battled the blaze overnight but were unable to save the building.

Scottish Fire and Rescue Service incident commander Colin Grieve said: "These were challenging conditions but firefighters worked extremely hard to bring the fire under control and we are now scaling back our resources."

Police Scotland's detective sergeant George Nixon added: "While the value of the damage has not yet been established this was a significant fire which has caused extensive destruction to a listed building.

"We are treating the fire as wilful and would appeal to anyone who saw anything unusual or suspicious in the area yesterday evening or has any information to contact police on 101 as soon as possible.

"This type of behaviour will absolutely not be tolerated. It goes without saying there is a significant risk of harm with such irresponsible behaviour."

Glen O'Dee was built as a place to treat tuberculosis and welcomed its first patients in 1900.

It closed in 1998 and Forbes Homes, which bought Glen O'Dee in 2007, tabled plans earlier this year to demolish part of the hospital and build houses and flats.