The disappearance of two South African men in Vietnam is under investigation by Gift of the Givers, which fears they may have fallen prey to an organ harvesting syndicate.

John Bothma and Mushfiq Daniels didn't know each other, but both South Africans had been teaching English in Ho Chi Minh City.

Gift of the Givers founder Imtiaz Sooliman said they shared mysterious acquaintances — two American women he described as having had contact with both men and who paid for their flights around South East Asia and treated them to lavish gifts.

“Both families approached me last week, which helped me, because I can compare the circumstances.”

Bothma, 22, disappeared in May, shortly before he was due to return home. Daniels, 28, vanished in July.

Sooliman said all evidence now pointed towards the men having become caught up in an organ harvesting ring, based on the prominence of the black market trade in Vietnam and the details surrounding their disappearance resembling those of past crimes.

“In February this year the authorities bust a major organ harvesting ring,” he said. “I strongly believe they are involved in this. It is a lucrative business in that part of the world.”