Italian news agency ANSA reports that the victims were a Dutch man and his three children. The mother was also with them and survived.

Adriano Fevre of the Valle d'Aosta mountain rescue corps could not immediately confirm the nationalities of those killed.

He said that the mountaineers - connected by ropes - were climbing Mont Dolent, which is part of the Mount Blanc massif.

The 4,810-metre Mount Blanc straddles Italy and France and attracts hundreds of climbers a year. Deaths are frequent.