A fire which has ravaged the historic Mackintosh Building has spread to "several properties", the fire and rescue service said.
Buildings including the O2 ABC have suffered "extensive damage" as flames and smoke poured into the night sky from the Glasgow School of Art building which has been undergoing a multi-million pound restoration project.
More than 120 firefighters were called to tackle the blaze after being called at just before 11.20pm on Friday night.
There are no reports of casualties, although residents living nearby have been evacuated from their homes.
Deputy Chief Officer Iain Bushell said: "This is an extremely challenging and complex incident, but the response and professionalism of our firefighters has been exceptional.
"The fire has taken hold several properties including the 02 ABC nightclub causing extensive damage.
"This will be a prolonged incident and crews will remain on the scene as they work to prevent further fire spread and damage."