Ailing anti-apartheid icon Nelson Mandela was spending a fourth day in hospital for more tests, as his wife Graca Machel said his trademark sparkle was waning. File photo by AP.

Johannesburg - Ailing former president Nelson Mandela was on Tuesday spending a fourth day in hospital for more tests, as his wife said his trademark “sparkle” was waning.

Looking calm in an interview, Graça Machel did not give details about Mandela's health status, just saying it was painful to see the nonagenarian “aging.”

“I mean, this spirit and this sparkle, you see that somehow it's fading,” she told ENews Central Africa (ENCA) on Monday in her first interview since Mandela was hospitalised at the weekend.

Government officials have said the former president is comfortable and does not face immediate danger, but they refuse to speculate on when he is likely to be discharged from a Pretoria military hospital.

Mandela, 94, was at the weekend admitted to hospital for tests that authorities say are expected of people of his age.

“To see him aging, it's something also which pains you. . . . You understand and you know it has to happen,” said Graça.

Mandela's grand-daughter Ndileka told the same TV network that he has taken to accept his condition.

“I think he takes it in his stride, he has come to accept that it's part of growing old, and it's part of humanity as such. At some point you will dependent on someone else, he has come to embrace it,” she said.

Defence Minister Nosiviwe Mapisa-Nqakula visited Mandela on Monday and said the revered statesman was “doing very, very well”.

The presidency said it was too early to give an update as they have to hear first from the doctors.

Journalists continued camping outside 1 Military Hospital on the outskirts of Pretoria on Tuesday morning. Soldiers were stopping and searching cars at the main entrance.

News crews, including an outside broadcast vehicle, were turned back at the entrance. Several journalists waited metres from the security checkpoint.

On Saturday, Zuma's office announced Mandela had been admitted to a Pretoria hospital for medical tests and care that was “consistent for his age”.

Zuma visited Mandela on Sunday morning at the hospital and found the former leader “comfortable and in good care,” presidential spokesman Mac Maharaj said in a statement. The condition the tests were related to had not been disclosed.

Mandela’s hospital stay was being watched by media around the world including the LA Times, the Telegraph, Hindustan Times, and Zimbabwe Independent.

The Washington Post included a CBS newsclip in which their reporter described him as having been “physically robust” but “mentally detached” at his 94th birthday celebration which they attended.

The Brisbane Times posted a video package of footage of him beaming with fellow African National Congress officials four years ago.

In February, Mandela spent a night in a hospital for a minor diagnostic surgery to determine the cause of an abdominal complaint. In January 2011 Mandela was admitted to a Johannesburg hospital for what officials initially described as tests, but what turned out to be an acute respiratory infection.

Mandela has had other health problems. He contracted tuberculosis during his years in prison and had surgery for an enlarged prostate gland in 1985. In 2001, Mandela underwent seven weeks of radiation therapy for prostate cancer.

Mandela, who spent 27 years in prison for fighting racist white rule, became the country’s first black president in 1994 and served one five-year term.

The Nobel laureate later retired from public life to live in the remote village of Qunu, in the Eastern Cape. He made a last public appearance when South Africa hosted the 2010 World Cup soccer tournament. - Sapa and AFP

Story update:

The eNCA apologised on Tuesday night for broadcasting an old interview with former president Nelson Mandela's wife Graca Machel.

“An eNCA report last night included a clip of Graca. She spoke of Mandela’s sparkle fading - we would like to clarify that this was from a 2009 interview and is not current,” the broadcaster said on its Twitter page.

“Machel was not responding in any way to Madiba's current hospital stay. We regret any confusion which may have been caused.”