Authorities say a Winnipeg man who allegedly killed his British friend in self-defence during an ayahuasca ceremony in Peru has been released from police custody.

Joshua Andrew Freeman Stevens, 29, killed his friend Unais Gomes, 26, after Gomes reportedly attacked him with a knife during the ceremony, police told Reuters. Stevens was freed after investigators concluded he acted in self-defence.

Amy Mills, a spokeswoman for the Canadian government responding to a request for information about the case, would only say that a Canadian has been released from detention in Peru.

"Canadian consular officials are in touch with local authorities and providing consular assistance," she wrote, adding they are not releasing a name due to privacy concerns.

Stevens 'filled with extreme sorrow'

Reached in Peru via social media, Stevens said he was OK.

"I loved Unais. I'm quite sore ... and beat up bad ... filled with extreme sorrow. But I'm alive and thankful," he said.

His fiancée, Sarah-Anne Allen, said Stevens is a kind and gentle person and the victim was his friend.

Sarah-Anne Allen says she has spoken with her fiancé, Joshua Andrew Freeman Stevens. She said he wants to return to Winnipeg as soon as possible. (Facebook) "He really loved Unais. He has told me they became much like brothers," said Allen, who is in Winnipeg. "He never would have done anything that was not completely necessary."

The attack happened during a ceremony near the jungle city of Iquitos on Wednesday night, Normando Marques, a police chief in the region, told Reuters news agency.

Allen told CBC News that she has spoken with Stevens and he is now staying at a hotel in Iquitos paid for by Phoenix Ayahuasca, the retreat centre where Stevens planned to take a spiritual journey.

"Authorities have his wallet and personal belongings. He is trying to have them mailed so that he can return home," said Allen.

Authorities say Stevens killed Briton Unais Gomes in self-defence at an ayahuasca ceremony in Peru. (Facebook) Stevens is always the first to offer help to anyone in need, she said.

"I want what is best for Joshua and his family, also what is best for Gomes's family. No one would have wanted this," she said.

What is ayahuasca?

Ayahuasca is a concoction of plants traditionally used by around 70 indigenous groups in the upper Amazon, and the formula varies between locations.

Banisteriopsis caapi, a vine, is always included as an ingredient, along with leaves from psychotria viridis (a bush from the same family as coffee). The plants are boiled together for several hours and then reduced.

Jim Sanders says he's used ayahuasca hundreds of times and has never seen anyone become violent while under the influence of the concoction. (Supplied) The plants give users psychedelic experiences when combined. Ayahuasca is not normally associated with violence.

Winnipeg filmmaker Jim Sanders said he has used ayahuasca hundreds of times since first discovering it about 11 years ago while filming a documentary in Peru.

The concoction is supposed to be used as a way of inducing spiritual experiences, Sanders said, adding he's never seen anyone turn violent when taking the substance while in the presence of a shaman.

"You take it to kind of visit your past, present and future and find inner peace and centredness and calmness," he said.

Sanders said he was shocked to hear about what happened between Stevens and Gomes. Sanders said he only takes the substance under the guidance of an experienced shaman.

"I think what is dangerous is who is running it and how it's being administered," Sanders said. "Ayahuasca itself is not dangerous, but who is running it and the intentions behind them is very dangerous."