Among well-wishers was erstwhile foe Mangosuthu Buthelezi, whose opposition Inkatha Freedom Party fought a fierce turf war with Mandela's African National Congress that saw an estimated 20,000 people killed in the years leading up to the first all-race elections in 1994 which installed Mandela as president.

"Through his unstinting work and dedication Madiba has managed to touch the hearts and souls of millions of people across the globe," Buthelezi said in a public birthday message to Mandela, affectionately known by his clan name Madiba.

The New National Party, which rose from the ashes of the National party that constructed the apartheid system of racial segregation and exploitation, praised the example Mandela has set to South Africans.

"The nation is indebted to former President Mandela for the selfless service he continues to give the nation and especially those in need. To Mr Mandela there is never a thought spared for himself, it is always for others," the party said of the man its political forbears saw jailed for 27 years.

After his release from jail, Mandela is credited with holding South Africa together as its first black president and averting a race war that many predicted after the end of white hegemony in 1994.

One of Johannesburg's smartest shopping malls, the newly-named Nelson Mandela Square, planned a birthday party for the father of the nation, asking children to send individual birthday cards to the Nobel Peace laureate.

One Sunday newspaper invited well-wishers to send birthday messages by mobile phone text message.

Mandela himself was due to spend the day at a private party with close friends and family at his home in Qunu in the impoverished Eastern Cape province.

Mandela said in June he was retiring from public life but stole the show last week in Bangkok at the world's biggest conference on HIV/AIDS -- which afflicts more people in South Africans than any other nation and has become his biggest campaigning issue.

Writing in South Africa's Sunday Independent newspaper, Mandela's white, Afrikaans-speaking personal assistant Zelda le Grange paid tribute to her boss and wished he could now spend quality time with his wife Graca Machel and his family.

"May you become as old as the oldest mountains. Thank you for being an inspiration to all of us," le Grange wrote.

"My wish for you on your 86th birthday is time."