Anti-apartheid icon Nelson Mandela is responding to treatment in hospital, the South African president has said.

Jacob Zuma told parliament on Wednesday that he was happy with the progress being made by the 94-year-old former president after a "difficult few days".

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

Mandela was admitted to hospital in Pretoria on Saturday with a recurring lung infection.

It is his fourth hospital stay since December, and there is a growing realisation among South Africa's 53 million people that they will one day have to say goodbye to the father of the "Rainbow Nation" that Mandela tried to forge from the apartheid-era.

His eldest daughter Zenani, who is South Africa's ambassador to Argentina, was seen on Wednesday entering the heavily guarded clinic 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 as have other family members.

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

Meanwhile, well wishers continued to arrive at his home in the Johannesburg suburb of Houghton to leave cards and offer their best wishes.

Wednesday is laced with meaning for South Africans as it marks the day 49 years ago that Mandela was sentenced to life in prison for conspiring to overthrow the apartheid government.

Mandela has a long history of lung problems since being diagnosed with early-stage tuberculosis in 1988, while in prison on wind-swept Robben Island, near Cape Town.

Source: Agencies