Six climbers have been killed after a "spike in temperatures" caused slabs of ice from "frozen waterfalls" to collapse in the Alps.

According to Alpine rescue authorities four of the mountain climbers had been scaling a waterfall in Gressony-Saint-Jean, in the Val d'Aosta region of Italy - near the Swiss border, when part of the ice wall gave way and detached from the mountainside.

Another climber - who was part of the group - was rescued by the Alpine rescue service after managing to reach a ledge above where the frozen waterfall cracked and detached.

In a separate incident two more climbers, both men, were also killed when an ice sheet broke off and crashed down on them near the town of La Grave, France, the mountain rescue service in Briancon confirmed.