A Canadian man who authorities say stabbed a British man to death in Peru after the pair drank a hallucinogenic brew has been released, police say.

Joshua Stevens, 29, was arrested in the Peruvian Amazon after the death of 26-year-old Unais Gomes on Wednesday.

A police chief in the city of Iquitos, Normando Marques, said Mr Stevens was released because all evidence showed he stabbed Mr Gomes in self-defence after the Briton tried to attack him with a knife.

Mr Stevens' fiancee, Sarah-Anne Allen, said all charges were dropped and the Canadian will return to his home country "soon".

"He is very shaken and sad, but he is coping," she said.

Canada's foreign affairs department said it is providing consular assistance to a citizen "released from detention in Peru".

It declined to identify the person in order to protect privacy.

A British foreign office spokesman said: "We can confirm the death of a British national in Peru on 16 December 2015.

"We are in contact with the local authorities and are providing consular assistance to the family at this difficult time."

The pair had been drinking a hallucinogenic plant brew known as ayahuasca at a spiritual retreat.

Ayahuasca, which is a combination of an Amazonian vine and dimethyltryptamine (DMT), gives users a psychedelic experience although it is not normally associated with violence.

In 2012 an American teen died after drinking ayahuasca during a ritual in the Madre de Dios jungle region of Peru.

A shaman later admitted trying to cover up the death by burying him in the grounds of the retreat.