At least 40 passengers were killed when a bus crashed down a mountainside in the Andes of southern Peru.

Another 10 people were injured in the accident as the bus travelled between Arequipa, Peru's second largest city, and the town of Santo Tomas.

Police said it fell 200m down the ravine, with recent rain and a mechanical failure being considered as causes.

There were also reports of overcrowding as people return home for Christmas.

Rescue efforts were difficult in the terrain, a local fire brigade member told AFP news agency.