Two fires that erupted overnight in apartment buildings in Switzerland left five people missing and 19 injured, police said on Friday.

In Thusis, in Switzerland's far-east, a "major fire" that broke out just after midnight "entirely burned" a building that housed a restaurant and residential flats, regional police in the canton of Graubünden said in a statement.

"The stairwell collapsed, so the roof of the building had to be opened with a crane," it said, adding that five people remained missing.

Police said 14 people had managed to escape the burning building. Eight of them were hurt, including two who were in serious condition, they said.

The injured had been transported to hospitals across Graubünden and in Zurich.