Mountaineers are being warned that the North Face of the Eiger has become too dangerous to attempt because its ice fields are melting.

Swiss Guides working on the mountain say that a combination of last summer's heatwave and poor snowfall since has caused a loosening of the permafrost that holds the face together.

The result is that the North Face, which has claimed more than 60 lives since the first successful ascent in 1938, is "falling apart", leaving climbers at severe risk of being injured or killed by falling rock and ice.

Hans Ulei, 38, a mountain guide from the nearby town of Interlaken, said: "We are telling people, 'Don't go on the North Face'. It is too dangerous.

"The mountain is falling down. These days I am often woken in the night by a sound like thunder. At 5am recently I heard that noise and when I looked from my window the North Face was half obscured by a grey cloud of powder from broken rocks." A spokesman for the Swiss Alpine Club said that recent climatic developments have made the 1938 route up the North Face too dangerous. "My advice to anyone contemplating the Eiger is not to try the North Face."

The first successful assault on the Eiger was made in 1938 when Heinrich Harrer and Fritz Kasparek, Anderl Heckmair and Ludwig Vorg climbed into history.

Telegraph.co.uk