South African President Jacob Zuma said on Wednesday he is happy with Nelson Mandela's progress, following what he called a "difficult few days" for the 94-year-old anti-apartheid hero who is being treated in hospital for a recurring lung infection.

Mandela, South Africa's first black president who ruled from 1994 to 1999, remained under intensive care at a Pretoria hospital for a fifth day on Wednesday battling a potentially deadly lung infection.

"We fully understand and appreciate the global interest in this world icon," Zuma told parliament.

"We urge South Africans and the international community to continue to keep president Mandela and the medical team in their thoughts and prayers."

Mandela's "serious" condition has reinforced a creeping realization among South Africa's 53 million people that they will one day have to say goodbye to the father of the "Rainbow Nation".

His eldest daughter, Zenani, who is South Africa's ambassador to Argentina, was seen entering the heavily guarded clinic on Wednesday where only close family members are being allowed.

Zenani as well as the elder statesman's two other daughters, Makaziwe and Zindzi, and his ex-wife, Winnie Madikizela-Mandela, have visited him daily this week.

His current wife, Graca Machel, called off a trip to London last week to be with her ailing husband.

Zuma will visit him "as soon as his diary allows", his spokesman told State radio. Wednesday was laced with meaning for South Africans as it marked the day 49 years ago that Mandela was sentenced to life in prison for conspiring to overthrow the apartheid government.

He spent 27 years in prison during white racist rule and was freed in 1990.

His latest health scare has been met with a growing acceptance that the Nobel Peace Prize laureate may be nearing the end of his life.

In Mthatha, a town near Mandela's home village of Qunu, Robert Slabbert said his death will be a big loss for South Africa and the world.

"He's changed the whole country so he's going to be really missed," he added.

Mandela has a long history of lung problems since being diagnosed with early-stage tuberculosis in 1988, while in prison on windswept Robben Island, near Cape Town. This is his fourth hospital stay since December.

Two months ago he was discharged after treatment for pneumonia.

In December he underwent surgery to remove gallstones as he recovered from a lung infection. In March he was admitted for a scheduled overnight check-up before returning to the hospital later that month for 10 days.

Reuters-AFP