A star-studded cast of artists helped Nelson Mandela to celebrate his 90th birthday with a giant concert in London on Friday in support of his global AIDS campaign.

Queen, Amy Winehouse and Annie Lennox were among the performers at the Hyde Park gig for the former South African president’s 46664 campaign, which was being broadcast around the world.

Addressing the crowd, a visibly frail Mandela, who had to be helped to the podium on stage, said: "Where human beings are being oppressed, there is more work to be done. Our work is for freedom for all.

"It is time for new hands to lift the burdens. It is in your hands now. I thank you," Mandela, who turns 90 on July 18, added.

Following an opening performance from Jivan Gasparyan,van Armenian duduk wooden flute master, US actor Will Smith introduced Anglo-Swedish rockers Razorlight.

Scottish singer Lennox, wearing a t-shirt reading "HIV positive," gave an impassioned speech about combating the virus.

"Don’t you think that every child should have the right to life?" she said, to huge applause. The Eurythmics vocalist then performed an acapella song with a choir from the Agape children’s orphanage in South Africa, where most residents have lost their parents to AIDS.

Queen and Paul Rodgers were set to rock the audience later before a finale of "Free Nelson Mandela" featuring Winehouse and the song’s writer, Specials keyboard player Jerry Dammers, plus all the artists. Mandela made headlines on by breaking his silence over the electoral violence in Zimbabwe, describing it as a "tragic failure of leadership."

Zimbabweans voted Friday in a run-off presidential poll with veteran incumbent Robert Mugabe left as the only candidate after violence against the opposition forced his rival Morgan Tsvangirai out of the race. Some campaigners have called on Mandela to elaborate on his comments.