Special events took place in South Africa and around the world on Wednesday to mark the 94th birthday of the country's former President Nelson Mandela.

July 18 has become known as "Mandela Day" and is seen as an opportunity to inspire people to take action to help change the world for the better.

Many people give 67 minutes of their time painting schools, planting trees and visiting orphanages and homes for the elderly, to honour Mandela's struggle.

The global icon, who has been in poor health since he was hospitalised a year ago with respiratory problems, was expected to spend the day with his close family and friends.

His last public appearance was in July 2010 at the final of the World Cup in Johannesburg Soccer City stadium.

Former US President Bill Clinton arrived in Mandela's home village of Qunu, in South Africa's Eastern Cape, on Tuesday, to surprise him ahead of his birthday.