At least 37 people were killed and 24 injured in southern Peru on Wednesday when a double-decker bus plunged into a ravine after colliding with a pick-up truck, officials said.

The accident in Arequipa is one of the worst in recent years in the South American nation, where road fatalities are frequent.

It occurred at around dawn along a stretch of the Panamericana Sur highway that connects Peru with Chile.

"We have a figure of 37 fatalities...in addition to 24 injured, said Walther Oporto, the regional health manager of Arequipa.

However, the death toll could rise because some people were seriously injured in the crash, he said.

The double-decker bus, operated by the Llamosas company, had departed on Tuesday night from Chala, a town in Caraveli province, and was heading to Arequipa, Peru's second-largest city. It was carrying more than 60 passengers.

The vehicle fell into a ravine approximately 200 metres deep after colliding head-on with the pick-up on a curve, according to local media reports that cited firefighters.

The bus rolled down the ravine and ended up on a riverbank.

Fire department spokesman Jack Paez said the rocky terrain was hampering rescue efforts.

"This accident...has brought grief to many families. There are elderly people and children" among the injured, he told TV Peru.

A priest was at the scene of the crash, praying beside bodies lined up on the riverbank, according to images released by the prosecutor's office.

"I ask for justice, that the full weight of the law be applied to the driver of the truck" thought to have caused the accident, a grieving relative who lost his father and brother told local media.

President Jose Jeri, in a message on X, extended condolences to those affected.

The truck's driver, who survived, was detained.

"The necessary procedures will be carried out to determine his responsibility in the accident," the Arequipa prosecutor's office said in a Facebook post.

The bus driver was killed, the Llamosas transportation company said.

At least two dozen police officers were coordinating with firefighters "on rescuing people, evacuating the injured, and recovering bodies," the Ministry of the Interior said. (AFP)