Footage on social media and Swiss television depicted the mudslide that occurred near Blatten in the southern Lotschental valley. Homes and structures were partially submerged in a thick layer of brown sludge.

Regional police said a 64-year-old man was reported missing, and search and rescue operations involving a drone with thermal camera were under way.

“Currently, about 90 percent of the village is either covered or destroyed, marking a significant disaster here in Blatten,” said Stephane Ganzer, the head of security for the southern Valais region, to local TV station Canal9.

The regional government said in a statement that a large chunk of the Birch Glacier above the village had broken off, causing the landslide which also buried the nearby Lonza River bed, raising the possibility of dammed water flows.

“There’s a risk that the situation could get worse,” Ganzer said, alluding to the blocked river.

He said the army had been mobilised after earlier indications that the movement of the glacier was accelerating.

At a news conference, Swiss Environment Minister Albert Rosti lamented “an extraordinary event” and said the government would take steps to help villagers who lost their homes.

In recent days the authorities had ordered the evacuation of about 300 people, as well as all livestock, from the village amid fears that the 1.5 million cubic metre glacier was at risk of collapse.

Local authorities were deploying by helicopter and across the area to assess the damage, Jonas Jeitziner, a spokesman for the Lotschental crisis centre, told The Associated Press.

Swiss glaciologists have repeatedly expressed concerns about a thaw in recent years, attributed in large part to global warming, that has accelerated the retreat of glaciers in Switzerland.