Nelson Mandela, left, waves from the stage as U.S. actor Will Smith smiles from behind at the 46664 charity concert in honour of Mandela's 90th birthday in London on Friday. ((AP Photo/Lefteris Pitarakis))

Greeted with a massive roar of applause, Nelson Mandela took the stage in London's Hyde Park Friday evening to speak to the tens of thousands of fans gathered to honour his 90th birthday.

"Friends, 20 years ago London hosted a historic concert which called for our freedom ... We are honoured to be back in London for this wonderful occasion [and] celebration," he said.

"But even as we celebrate, let us remind ourselves that our work is far from complete. Where there is poverty and sickness, including AIDS, where human beings are being oppressed, there is more work to be done. Our work is for freedom for all."

Some have suggested this week that the London concert could mark one of the South African icon's final major public appearances. Mandela's own comments at the concert hinted at this.

"We say tonight, after nearly 90 years of life, it is time for new hands to lift the burdens. It is in your hands now. I thank you," he concluded.

The celebrity-studded event to honour Mandela is the latest fundraiser for the HIV/AIDS charity 46664 — named for the number he wore during his 27-year imprisonment in South Africa's apartheid era.

Annie Lennox, Amy Winehouse, Queen, Josh Groban, Johnny Clegg, Papa Wemba, Simple Minds and the Soweto Gospel Choir were among the host of top international recording acts on the bill for the four-hour show, hosted by U.S. actor Will Smith.

Troubled 24-year-old soul singer Winehouse, who was hospitalized last week, closed the show, singing The Specials' 1984 tune Free Nelson Mandela.

Though Mandela's birthday is actually July 18, Friday's date was chosen to commemorate the 20th anniversary of the 1988 Wembley Stadium concert that called for his freedom from prison. He was eventually released in 1990.

"I can't believe it's 20 years ago," said The Specials founder Jerry Dammers, who added that writing the song led to his becoming involved with Artists Against Apartheid and working on other charity concerts.

"This is great. It's [Mandela's] 90th birthday and we're celebrating that."

Queen guitarist Brian May described the concert as "very much about spreading Nelson Mandela's message to the next generation, and I'm very happy to be a part of it."

Bono and The Edge of U2 also recorded a version of Happy Birthday that was shown during the concert, organizers said.

Mandela arrived in London on Monday for a week of birthday celebrations, including a private meeting with the Queen and dinner Wednesday night with British Prime Minister Gordon Brown, former U.S. president Bill Clinton, talk show host Oprah Winfrey and actor Robert De Niro.

Highlights of Friday's concert will be broadcast on CBC-TV and CBC Radio 2 and streamed from on Friday evening beginning at 7:30 p.m. The full concert will air on CBC digital channel bold on Saturday at 1 p.m. and 10 p.m. ET. It will also be available on until July 27.

With files from the Associated Press