SOUTH Africa's anti-apartheid hero Nelson Mandela is comfortable and able to breathe without problems as he continues to respond to treatment in hospital for a recurrence of pneumonia.

After the revered 94-year-old statesman spent a third night in hospital, President Jacob Zuma's office said doctors had drained excess fluid from his lungs to tackle the infection.

"This has resulted in him now being able to breathe without difficulty. He continues to respond to treatment and is comfortable," the office added.

In the first detailed mention of his medical condition since his latest hospitalisation, the third in four months, the presidency said the Nobel Peace Prize laureate and former South African president had "developed a pleural effusion which was tapped".

Previous bulletins since he was taken to hospital late on Wednesday have reported him being in "good spirits".

They have appeared to indicate that the recurrence of Mandela's lung infection is being successfully treated.

Mandela, who became South Africa's first black president in 1994 and stepped down five years later, has been mostly absent from the political scene for the past decade. But he remains an enduring symbol of the struggle against racism.

Global figures such as US President Barack Obama have sent get-well messages and South Africans have included Mandela in their prayers on the Easter weekend.

Mandela is revered worldwide for leading the struggle against white minority rule, then promoting racial reconciliation when in power.

His fragile health has been a concern for years as he has withdrawn from the public eye and mostly stayed at his affluent homes in Johannesburg and in Qunu, the rural village in the destitute Eastern Cape province near his birthplace.

South Africans have been following the official medical bulletins closely. "He is the father of the nation, our Abraham Lincoln, our George Washington," said economics student Curtis Richardson, 19, as he visited Nelson Mandela Square in a Johannesburg shopping centre with friends.

Mandela remains a global inspiration. "If he dies, it will be a tragedy, because he's such a symbol," said Kagisho Paterson, 19, a visitor from Britain, snapping photos near a towering statue of Mandela in the square.

English Premier League football team Sunderland FC designated Saturday "Nelson Mandela Day" to kick off its new deal supporting the ex-president's charitable foundation.

Mandela's ruling African National Congress (ANC) is still the dominant force in South African politics, but critics say it has lost the moral compass bequeathed it by the previous generation of anti-apartheid freedom fighters.

Under such leaders as Mandela, along with the late Walter Sisulu and Oliver Tambo, the ANC gained wide international respect when it battled white rule.

Once the yoke of apartheid was thrown off in 1994, the ANC began governing South Africa in a blaze of goodwill from world leaders who viewed it as a beacon for a troubled continent and world.

Almost two decades later, this image has dimmed as ANC leaders have been accused of indulging in the spoils of office, squandering mineral resources and engaging in power struggles.

Mandela was in hospital briefly earlier this month for a check-up and spent nearly three weeks in hospital in December with a lung infection and after surgery to remove gallstones.

He has a history of lung problems dating back to when he contracted tuberculosis as a political prisoner.

A Nigerian visitor to Johannesburg, civil engineer Gregory Osugba, 35, called Mandela "an icon of greatness and freedom" for the entire African continent and the world.

"When he goes - the symbol will remain," he said.