The bus, which had more than 50 people on board, tumbled off the road in the early hours of the morning on the Interoceanic Highway, which connects Peru with Brazil.
"We have so far recorded 10 deaths after a bus fell into a 100 metre (325 feet) gorge," said Jose Ramirez, an police official in Puquio, the closest town to where the accident took place.
The bus was traveling from the capital Lima to Querobamba, Sucre province, which is located over 3,500 metres above sea level.
There were two other deadly bus crashes in Peru in January and February, which killed 97 people in total.