Former South African president Nelson Mandela has turned 95 in hospital, as events take place around the world to celebrate his birthday.

South Africans have been asked to mark Mr Mandela's 67 years of public service by spending 67 minutes on charitable acts. Volunteers will paint schools, biker gangs will clean streets and politicians will devote time to worthy projects.

Elsewhere in the country, social workers, military commanders and others joined in planting trees, painting hospices, and donating food, blankets and other basic necessities in poor areas. Doctors also administered eye tests and other medical treatments to the needy.

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The UN has declared 18 July 18 as Nelson Mandela International Day as a way of recognising the Nobel Peace Prize winner's contribution to reconciliation. A procession was held in India to honour Mr Mandela. In Washington, US congressional leaders planned a ceremony later.

Mr Mandela remains in a critical but stable condition with a lung infection in a Pretoria hospital. South African President Jacob Zuma said his condition was improving.

"Madiba remains in hospital in Pretoria, but his doctors have confirmed that his health is steadily improving," Mr Zuma said in a statement using Mandela's traditional clan name.

"We thank all our people for supporting Madiba throughout the hospitalisation with undying love and compassion," he said.