Italian officials have been forced to close roads and evacuate mountain huts in the northwest of the country over fears a huge chunk of the Mont Blanc glacier could break away.
Authorities in Courmayeur, Italy have warned a 250,000 cubic metre block of ice from the Planpincieux glacier, on the Grandes Jorasses mountain, might collapse imminently.
The glacier, on the Italian side of the Mont Blanc massif — which is western Europe’s highest mountain range — has accelerated its movement from 50 to 60 centimetres a day in recent months.
"These phenomena once again show how the mountain is going through a period of major change due to climate factors and, therefore, it is particularly vulnerable," Courmayeur Mayor Stefano Miserocchi said.
“In this case it is a temperate glacier particularly sensitive to high temperatures,” he added.
There is not believed to be any threat to tourist facilities, which draw hundreds of thousands of visitors a year to the French-Italian border.
At the UN General Assembly, where climate change has been near the top of the agenda, Italian President Guiseppe Conte warned of the potential catastrophe.
"Just now we have heard the news of a glacier on the Italian side of Mont Blanc, the highest mountain — the most majestic in the Alps — which risks collapsing,” he said.
"This is an alarm before which we cannot be indifferent in the illusion that it doesn't regard me, you, that it is something far away in time or in space.
"Instead it should shake all of us and mobilise us.”