A 40-year-old Italian climber from Milan died in a fall after reaching a height of 3,000 metres (9,840 feet) in the Coolidge Couloir which leads to Mount Pelvoux, a mountain in the Massif des Ecrins.
Emergency services attempted to revive him but he was pronounced dead.
Two French women aged 48 and 54 were killed as they climbed with a mountain guide towards Breche de la Meije, a high mountain pass also in the Massif des Ecrins in southeast France.
"The man was roped with the two women and was in the lead. When he tried to secure himself on a block of rock, it broke off...," the Gap prosecutor's
office said in a statement.
The 32-year-old guide survived but was injured and taken to hospital in Grenoble.
A climber died in another incident on Mont Blanc although there were no further details on the accident.