Police in Switzerland say four people are dead after an avalanche hit a group of skiers in the south-east of the country.

Police in the canton of Graubünden said the avalanche on the slopes of the Piz Vilan mountain Saturday afternoon swept away seven members of a nine-strong group of skiers.

Rescuers recovered three bodies and four seriously injured people, who were flown to hospitals in St. Gallen, Zurich and Chur. Police say a fourth person later died at a hospital.

There was no immediate word on what triggered the avalanche.