Nelson Mandela, the icon of the anti-apartheid movement and South Africa's first black president, celebrated his 90th birthday Friday as tributes poured in from around the world.

While Mandela employed his usual self-deprecating sense of humour, referring to himself as a retired old man, South Africans hailed him as the father of the nation and an unstoppable force for good even though he has long retired.

As newspapers printed special "Madiba" supplements, preparations were under way for celebratory events around the country, including a boxing tournament in honour of the one-time amateur pugilist.

Mandela was due to host a major bash with 500 guests on Saturday at his rural homestead in the Eastern Cape but spent Friday with his family and wife Graca as the couple also celebrate their 10th wedding anniversary.

"We are honoured that you wish to celebrate the birthday of a retired old man who no longer has power or influence," said Mandela in a pre-recorded birthday message.

"We wish you well wherever you are. We are all celebrating and we thank you for joining me in those celebrations."

Mandela, who served as president from 1994-99 after spending nearly three decades behind bars, has proved a tough act to follow and his birthday has been used by many commentators as an opportunity to draw an unflattering comparison with his successor Thabo Mbeki.

"The sweet celebration of a life of leadership, service and generosity is mixed with the sour taste of a legacy being polluted in front of the old man's tired eyes," the Mail and Guardian said in an editorial.

Mbeki, due to attend Saturday's party here in Qunu, paid generous tribute to Mandela as "the embodiment of what human beings should be in themselves and to others".

Former Springbok skipper Francois Pienaar, whose on-pitch celebrations with Mandela after winning the 1995 rugby World Cup epitomised the spirit of post-apartheid reconciliation, thanked him "for the inspiration you gave a nation".

F.W. de Klerk, the last president of the apartheid era South Africa, described Mandela as one of the greatest figures of the 20th century.

"After his inauguration, Nelson Mandela used his personal charm to promote reconciliation and to mould our widely diverse communities into an emerging multicultural nation. This, I believe, will be seen as his greatest legacy," de Klerk said.

In Qunu, villagers said they were honoured by Mandela's presence even if they have not been invited to Saturday's party.

"I have heard that we are not invited but I am going to put on my best suit and stand at the gate just to catch a glimpse of him," said 60-year-old Thandile Geledwa.

"This is a big day for our village especially for Madiba. It is always nice to hear our place being mentioned in same breath as his name. This makes his birthday our birthday too," said an elated Asive Joyini.

Photographers and journalists were camped outside the home where a gigantic white marquee has been pitched in anticipation of the event.

Three cows are to be slaughtered for the festivities, with the banquet menu featuring traditional food such as tripe and sheep's heads.

Celebrations of Mandela's birthday have been ongoing for several weeks, including a massive concert last month in Hyde Park, London, to raise funds for his AIDS charity while limited edition coins and stamps bearing his image have been launched to also generate money for his charitable foundation.

Mandela retired from public life four years ago but has continued to be involved with his foundation, raising millions of dollars for AIDS charities and to help underprivileged children.