Alpine rescue authorities said a combination of the sun and a sudden spike in temperatures melted the ice from frozen waterfalls, causing it to detach.
Four climbers killed in Italy were scaling a waterfall in Gressony-Saint-Jean, in the Val d'Aosta region near the border with Switzerland, when part of the ice wall gave way.
Alpine teams were able to rescue a fifth climber because he had apparently already reached a ledge above where the frozen waterfall cracked off, the head of the Val d'Aosta Alpine rescue service, Adriano Favre, told Italian media.
In the French Alps, two men were killed near the town of La Grave when an ice sheet broke off and crashed down on them, said Julien Michon, of the mountain rescue service in Briancon.
Mr Michon said the weather there was unusually warm and sunny.
The climbers' bodies were brought to Briancon.
