Rescue crews are seeking eight people from Germany, Austria and Switzerland who have been missing for more than a day after a landslide struck a remote Swiss valley, police said on Thursday.

"In the region of Val Bondasca, eight people who were there at the time of the landslide have not been found," the Graubunden cantonal police said in a statement.

The Wednesday morning landslide sent mud, rocks and dirt flooding into the village of Bondo as authorities had evacuated around 100 people from the village and airlifted hikers from nearby huts in the eastern canton of the Grisons.

Police said they were unable to reach eight people in the area, six of whom had been reported missing by relatives, despite intensified searches by teams including an army helicopter.

"The missing persons are nationals from Germany, Austria and Switzerland," the police said.

Images showed a broad swathe of farmland covered in a grey, moving mass, with mud partially engulfing some buildings.

Police said 12 farm buildings, including barns and stables, had been destroyed by the flow of debris.