Three people are missing after floodwaters swept through the south-eastern Swiss town of Misox in the alpine valley of Graubünden - also known as Grisons.

A massive thunderstorm on Friday night caused rivers to break their banks, flooding streets and causing several dozen residents to be evacuated.

Four were initially reported missing, but a woman was found under rocks and taken to hospital in the city of Lugano. Rescuers are still searching for a couple and a woman who may have been in their homes when the flooding occurred, police said.

Further west, the alpine resort of Zermatt has been isolated by floodwaters.

Footage from the town, which lies at the base of the iconic Matterhorn mountain, showed floodwaters raging through the streets on Friday.

The Swiss government's weather service said 124 mm (4.88 in) of rain had fallen in the area on Friday - most of it over a one-hour period.

"This concentration of rain happens only once every 30 years," a spokesman for the service said.

Train links between Visp and Zermatt have been suspended, and theroad between Täsch and Zermatt has been closed, leaving the resort completely inaccessible.

Authorities had prepared for some overflow, restricting public access to the banks of the Rhône and its offshoot rivers from Friday. (BBC)