Forty-nine people died of dehydration in a remote part of the Sahara desert in north-west Niger after the truck transporting them broke down, authorities said on Thursday.

The dead were among a group returning from Mali for a Muslim festival when they ran short of water, the Agadez governorate said in a post on Facebook.

The 49 people "died of thirst in a remote area more than 80 kilometres west of Assamaka", added the statement.

Assamaka is a main crossing point between Niger and Algeria but also close to the Mali frontier.

"Deprived of water and unable to repair the vehicle despite the efforts of the driver, his assistants and the passengers, the travellers found themselves trapped in the heart of a hostile environment where extreme temperatures and the absence of supply points make survival extremely difficult," the governorate wrote.

Two people managed to survive after walking more than 50 kilometres on foot to a nearby water source and then onwards to Assamaka, where the pair were able to alert the authorities and a delegation was sent to the scene, the governorate said.

The 49 victims were buried in mass graves.

On the way back, the delegation came across another vehicle that had been stranded for three days. The 60 passengers were rescued.

Such events, the governorate wrote, serve as a reminder of “the human cost of travelling through one of the most hostile environments on the planet”.

The desert zone is a known transit point for migrants seeking to get from African nations to Europe and many have died there from thirst or starvation.

(with newswires)