Some 12 million children across South Africa have sung a specially composed song as part of official celebrations for Nelson Mandela’s 94th birthday.

It was among an outpouring of well wishes from around the world.

The former South African president is believed to have spent a “quiet” day with family at home in the village of Qunu in the Eastern Cape.

The man fondly referred to by his clan name, Madiba, now only appears rarely in public.

He spent 27 years in jail for leading an armed anti-apartheid campaign and became president in 1994.

Since his retirement from public life, the frenzy that erupts around his birthday each year has only grown – with some South Africans complaining his name has been debased by its association with a proliferation of causes.

The day began with some 12 million schoolchildren singing a birthday song including the line, “We love you father”.

Throughout the day, statements were released by politicians, campaigners and union leaders – with Human Settlements Minister Tokyo Sexwale urging fellow South Africans to celebrate their fortune to “live in the same country breathing the same air under the same sun with Nelson Mandela”.

Mr Mandela’s granddaughter, Ndileka Mandela, told Sowetan Live that the Mandela family would celebrate with a lunch including Mr Mandela’s favourite food.

“The big lunch will be at 4pm where we will present him with a cake. Our 67 minutes is a way of giving back to him, and that is our birthday gift to him,” she said.

“We will probably have food like [local corn dish] samp and tripe, his favourite food.”

On Tuesday Mr Mandela met former US President Bill Clinton on Tuesday.

Mr Clinton, accompanied by his daughter Chelsea, opened a new library for the No-Moscow Primary School in Qunu, ahead of his meeting with Mr Mandela.

“When I think about Mandela I always think about someone committed to the future,” Mr Clinton said.

US President Barack Obama and his wife, Michelle Obama, also paid tribute ahead of Mr Mandela’s birthday.

The US first couple hailed Mr Mandela’s “extraordinary life and steadfast commitment to the principles of democracy and reconciliation”.

The BBC’s Milton Nkosi in Qunu says that across South Africa, Mr Mandela’s birthday is traditionally celebrated with the poor communities receiving help from those who are more fortunate.

Our correspondent says to celebrate the number of years Mr Mandela spent in public life, people are encouraged to spend at least 67 minutes of their time helping those who are less fortunate.

But some have criticised the UN-backed initiative as a token gesture used to assuage the guilt of those at the top of a deeply economically polarised society.

If Mr Mandela knew how poorly the country’s schools were performing, “he would be crying”, said Nobel laureate Archbishop Desmond Tutu.

Mr Mandela stood down as South Africa’s president in 1999 after serving one term, handing over to Thabo Mbeki.

After leaving prison in 1990, he led the African National Congress party to a landslide victory in 1994 – the first time South Africa’s black majority was allowed to vote.

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