Vietnam says it will recall one of its diplomats from South Africa after she was filmed in an apparent illegal purchase of a rhinoceros horn.

A TV crew accompanying government investigators filmed an agent for a gang of poachers meeting the woman outside Vietnam's embassy in Pretoria.

They filmed the agent handing the horn to the diplomat, who then took it inside the embassy building.

Vietnam's Foreign Ministry said it had recalled her to "clarify the affair".

Vietnam's ambassador to South Africa, Tran Duy Thi, told the BBC that action had to be taken.

"She did it right at the front steps of the embassy," he said. "You see, they filmed the Vietnamese flag as she was doing it -how shameful! There must be a sanction."

More than 40 rhinos are said to have been killed in South Africa this year.

Conservationists say Vietnamese syndicates are heavily involved in the illegal trade of their horns.

Crushed rhinoceros horn is a prised ingredient in traditional East Asian medicine, where it is used to treat fever and high blood pressure.