For desperate Vietnamese cancer patients ground rhinoceros horn is seen as an elixir of life -- a medically unproven and illegal obsession that threatens the very survival of the world's wild rhinos.

The substance, which shares the same protein found in human fingernails, sells for thousands of dollars an ounce in Vietnam. Soaring demand has led to a bloodbath in South Africa as poachers kill record numbers of the creatures.

“I was diagnosed with stomach cancer nine years ago. I've tried everything including rhino horn powder every day. Now, doctors have told me I'm in a stable condition,” wealthy Hanoi-based octogenarian Nguyen Hung told AFP.

Targeted medical studies have shown that rhino horn has no medical benefits. Two cancer patients taking rhino horn as part of their treatment who were contacted by AFP for this story died before interviews could be arranged.

Tran Thi Hiep, a 60-year-old retired official who discovered a tumour on her neck six years ago and has been using rhino horn, said that traditional Vietnamese culture encourages people to try every possible treatment.

On Hanoi's Lan Ong street, a bustling hub for traditional medicine, nearly every shop sells special ceramic dishes that have a coarse surface on which rhino horn is gently grated down.

“Rhino horn is used to prevent and to cure cancer... You need to grind it into a powder before serving it with water or alcohol,” Tran Thu Thao, a specialist in Vietnamese traditional medicine, told AFP.

A hundred grams costs up to 120 million dong ($5,000) on the black market, she said.

There is also a huge trade in counterfeit horn as local demand far outstrips supply and Thao said well-known traders have months-long waiting lists for the genuine substance.

Due to this  surging demand for rhino horns in Asian traditional medicine, decades of conservation efforts to save rhinos are coming undone. - Photos by AFP.