Johannesburg - South Africans on Wednesday sang happy birthday to their revered liberation hero Nelson Mandela, who turned 94.
People called in to radio stations and posted messages on social networking sites wishing the first black president of a democratic South Africa a happy day, which he would likely spend away from the spotlight with his close family and friends.
The ageing leader has grown frail and was hospitalised twice since early 2011. Relatives say his health is as good as can be expected for a man of his age.
July 18 is marked as International Nelson Mandela Day, a UN-backed event. People are asked to spend 67 minutes of their time on this day to helping their fellow people in honour of Mandela's 67 years of public service.
"There is no more fitting tribute to a man who has demonstrated to the world the extraordinary power of non-violence, of tolerance, and of unwavering service to our fellow men and women," US President Barack Obama said in a statement.
"Nelson Mandela's personal story is one of unbreakable will, unwavering integrity, and abiding humility," the US leader said, noting that his own family had been inspired by the freedom icon.

Alex Ferguson sings for Madiba
Former president Bill Clinton visited Madiba in his ancestral village of Qunu at the weekend, as part of a tour of southern Africa.
Alex Ferguson, who is also visiting the country with Manchester United, which is set to play a football match against Ajax Cape Town, appeared on national television to sing happy birthday and cut a cake.
Mandela published his autobiography, A Long Walk to Freedom, in 1995. The book details his early life through his 27 years in prison, after the white-minority regime sentenced him to jail for his role in the struggle against apartheid.

He was released from prison in February 1990.
The liberation icon - whose name became the symbol of struggle in the final years of minority rule - was elected president of South Africa in 1994 in the first all-race vote, serving for just one five-year term before stepping down.
In the lead up to the transformation to democracy, Mandela led talks with the apartheid regime, insisting on making peace with his former jailers