Johannesburg: Around 12 million school children all over South Africa on Monday sang "Happy Birthday" to anti-apartheid icon Nelson Mandela as he celebrated his 93rd birthday, echoing the sentiment of people across the world.

The students sang a special version of "Happy Birthday" before lessons began on Monday.

Mandela spent his birthday with his family at his childhood village Qunu in the Eastern Cape province, a news daily reported.

In a birthday message, South African President Jacob Zuma, said Mandela had laid a solid foundation for the country and it was now up to South Africans to continue his legacy.

"We have achieved a lot, but we must still work further to eradicate poverty and improve especially the lives of children, because Madiba loves them so much. Most importantly, we must spread love, ubuntu (humanity to others), humility and selflessness around us," Zuma said.

US President Barack Obama and wife Michael also saluted anti-apartheid icon Nelson Mandela on his 93rd birthday, saying he set the standard for service delivery by civil servants worldwide, the daily reported.

The Nobel Peace Prize laureate led the struggle to bring down South Africa's system of white minority rule and discrimination against blacks and in 1994, he became the country's first black president.

The United Nations designated the former leader's birthday as Nelson Mandela Day in 2009, with a call for individuals to do 67 minutes of community service to represent the number of years he spent in politics.