A South African sign-language interpreter accused of miming nonsense as world leaders paid tribute to Nelson Mandela defended himself as a "champion" signer on Thursday, but said he suffered a schizophrenic episode during the event.

The interpreter, 34-year-old Thamsanqa Jantjie, told Johannesburg's Star newspaper he started hearing voices and hallucinating while on stage, resulting in gestures that made no sense to outraged deaf people around the world.

"There was nothing I could do. I was alone in a very dangerous situation. I tried to control myself and not show the world what was going on. I am very sorry. It's the situation I found myself in," he told the paper.

The government admitted Jantjie was not a professional interpreter but played down security concerns at his sharing the podium with world leaders including US President Barack Obama at the memorial on Tuesday.

"He was procured. He did not just rock up," Deputy Disabilities Minister Hendrietta Bogopane-Zulu told a news conference. "Did a mistake happen? Yes. He became overwhelmed. He did not use the normal signs. We accept all that."

After the memorial, South Africa's leading deaf association denounced him as a fake, making up gestures to be put into the mouths of Obama and his South African counterpart Jacob Zuma.

Jantjie said he did not know what triggered the attack and said he took medication for his schizophrenia.

Besides the security issues, the controversy has cast a shadow over South Africa's 10-day farewell to its first black president, who died a week ago aged 95.

It also heaps more pressure on Zuma, who is fighting a slew of corruption allegations against him and his administration and who was booed by the crowd on Tuesday.

Footage from two large African National Congress (ANC) events last year shows Jantjie signing on stage next to Zuma, although the ruling party said it had no idea who he was.

Company "vanished"

In a radio interview, Jantjie said he was happy with his performance at the memorial.

"Absolutely, absolutely. I think that I've been a champion of sign language," he told Johannesburg's Talk Radio 702.

When contacted by Reuters, he said he could not understand why people were complaining now, rather than after other events. "I'm not a failure. I deliver," he said.

The publicity surrounding Jantjie's unconventional gestures - experts said he did not know even basic signs such as "thank you" or "Mandela" - sparked a frenetic hunt for him and his employers.

Jantjie said he worked for a company called SA Interpreters, hired by the ANC for Tuesday's ceremony at Johannesburg's 95,000-seat Soccer City stadium.

Attempts by Reuters to track down the company were unsuccessful. Bogopane-Zulu said its management had fled the glare of publicity, with the suggestion that it had been providing sub-standard interpreters for some time.

"We managed to get hold of them, and then we spoke to them wanting some answers and they vanished into thin air," she said. "It's a clear indication that over the years they have managed to get away with this."

The death of Nobel peace laureate Mandela has led to an outpouring of grief and emotion, combined with celebration and thanksgiving, among his 53 million countrymen and millions more around the world.

Thousands more mourners queued to say goodbye to Mandela in Pretoria, although that too has not been without its problems.

In the absence of sufficient drinking water and toilets, several people passed out on Wednesday, and on Thursday social media reports said some mourners had photographed Mandela's body, defying the wishes of his family and the government.

But the Department of State Security said in a statement that a purported photograph of Mandela's remains was a fake and urged people to delete it. It said there were no plans to release an official photograph of Mandela lying in state.

His body will lie in state for a third day on Friday before being flown to the Eastern Cape to be buried on Sunday at his ancestral home in Qunu, 700 km (450 miles) south of Johannesburg.