LYON (AFP) - Worries mounted on Thursday (Aug 10) for a 35-year-old Japanese climber who sent an SOS message after getting trapped in bad weather on the Mont Blanc mountain in France.

The man posted a message on social media on Wednesday saying he was coming down from the 4,810m-high summit of western Europe's highest peak but needed help.

Rescue helicopters are unable to fly because of poor visibility and rain, with conditions only expected to improve on Saturday.

Patrice Ribes, head of the local police rescue service, said the climber "could survive several days" providing he had found shelter and had enough water.

"As soon as we can, we'll go looking for him," he added.