Judge Seeraj Desai (right) said he was innocent

Winnie Madikizela-Mandela says it is difficult to believe that the respected judge could rape somebody.

She was also at the anti-globalisation conference where Seeraj Desai, 53, allegedly raped an Aids campaigner in her twenties.

Police say Mr Desai has admitted having sex with the woman but insists it was by mutual consent.

His lawyer says that he is the victim of blackmail, reports the AFP news agency. Ms Madikizela-Mandela visited Mr Desai in the Bombay prison where he is being held after bail was denied.

"Serajuddin is a long-time friend and a comrade in the freedom struggle," she said.

"I have faith in the Indian judiciary and I'm sure he will be vindicated."

Media scrum

The BBC's Barnaby Phillips in Johannesburg says the Aids campaigner, who accused Mr Desai of rape, has arrived in South Africa where she has raised enormous media attention.

She however managed to evade a battery of journalists who had pitched camp at the airport waiting to interview here.

The campaigner claims to have gone to visit the Cape Town judge at his hotel room at the Taj President Hotel in the Cuff Parade area of Bombay, at 0300 to discuss the next day's programme.

She alleges that after some kissing and holding, Mr Desai raped her.

She contacted her husband in South Africa who wasted no time in telephoning a Johannesburg radio station.

The six-day World Social Forum attracted about 100,000 participants.

They are discussing issues ranging from the environment to the US-led occupation of Iraq.

Forum spokesman Gautam Mody said: "The incident has saddened and shocked us."

South African foreign affairs department spokesperson Nomfanelo Kota said it was following up the matter.