A new landslide has forced more evacuations from a valley in the Swiss Alps where eight hikers were buried in a barrage of boulders and mud a week ago, authorities said Friday.

A violent thunderstorm and heavy rains lashing the Piz Cengalo at the Italian border set already unstable landmass in motion, sending rocks and sludge down the mountainside late Thursday.

The river of mud followed the same path as the giant landslide that hit the area last week, when eight hikers from Germany, Austria and Switzerland disappeared.

Thursday's landslide flowed into Bondo and neighbouring villages, destroying houses and roads in its path, municipal authorities in the Bregaglia valley said in a statement. 

Most residents in the small hamlet of Spino had left on their own, but two elderly people were evacuated by emergency workers. No one was injured, it said.

In Bondo, where around 100 people were evacuated after last week's landslide, several houses were completely destroyed.

Houses were also destroyed in the village of Promontogno and some houses were damaged in Spino.

Authorities said it remained unclear exactly how big the latest landslide had been, but said it appeared to have been quite large.

They had warned Bregaglia residents earlier Thursday that the heavy rains made more landslides in the region likely.

The initial landslide that hit the area On August 23 set four million cubic metres (141 million cubic feet) of mud and debris in motion.

The event was so severe that the vibrations set off seismometers across Switzerland, measuring the equivalent of a 3.0 magnitude earthquake, according to the Swiss Seismological Service.

Authorities have warned that up to one million cubic metres of rock and dirt remain unstable and could still come tumbling down Piz Cengalo.