The frail 94-year-old, one of the towering figures of modern history, was admitted late on Wednesday for his third hospitalisation in four months.

Doctors drained a build-up of fluid, known as a pleural effusion or "water on the lungs", that had developed from the lung infection.

"This has resulted in him now being able to breathe without difficulty," President Jacob Zuma's office said in a statement on Saturday.

On Sunday morning, Zuma's spokesperson Mac Maharaj said he didn't have another update on the anti-apartheid icon's health, as he awaited a report from the doctors.

"I have said he is responding (to treatment), making steady progress," said Maharaj.

It was unclear how long South Africa's first black president would remain hospitalised.

Mandela's recent health troubles have triggered an outpouring of prayers but have also seen South Africans come to terms with the mortality of the revered Nobel Peace Prize winner.

On Sunday Christians celebrated Easter Sunday offering prayers for Mandela.

"Yes, we are concerned that he is ailing, and he is getting worse, naturally we should be concerned. I think this is the question in the back of many of our minds, when is the end? Is he going to die?" Father Sebastian Rossouw, an assistant parish priest at the Regina Mundi Catholic Church in Soweto township told parishioners.

"We should rather celebrate what he stood for, and what he continues to stand for, that he has been an icon of peace, an icon of service."

The Regina Mundi church was once a pivotal centre in the resistance against apartheid, offering shelter to activists.

The former president is idolised at home, where he is seen as the architect of South Africa's peaceful transition from white minority-ruled police state to hope-filled democracy.

Nearly 20 years after he came to power in 1994, Mandela remains a unifying symbol in a country still riven by racial tensions and deep inequality.

It is the second time this month that Mandela has been admitted to hospital, after spending a night for check-ups on March 9.

That followed a nearly three-week hospital stay in December for another lung infection and gallstone surgery, his longest since he walked free from jail in 1990.

He was diagnosed with early-stage tuberculosis in 1988 during his 27-year jail term and has long had problems with his lungs. He has also had treatment for prostate cancer and has suffered stomach ailments.

Keertan Dheda, professor of respiratory medicine at the University of Cape Town, said a pleural effusion was the accumulation of water between the lining covering the lung and that of the chest wall.

Having the fluid tapped was a minor procedure, he said.

"One can drain the fluid with a needle and a catheter and in some cases that's all that's needed," he said.

Other cases required the fluid to be chemically broken down if it had formed pockets or a small operation if infected.

"The older you are, the longer pneumonia takes to get better," said Dheda, adding that mortality was also higher.

"It takes a bit longer, everything is a bit slower and a bit more complicated the older you get."

French pulmonologist Jean-Christophe Renaud said Mandela had a good constitution and could recover well.

"But at 94, everything is serious, especially taking into account his previous medical history."

While Mandela's legacy continues to loom large, he has long since exited the political stage and for the country's youthful population he is a figure from another era who served as president for just one term.

He has not appeared in public since July 2010.

Labour unrest, high-profile crimes, grinding poverty and corruption scandals have effectively ended the honeymoon enjoyed after Mandela ushered in the "Rainbow Nation", but his decades-long struggle against apartheid still resonates.  – Sapa-AFP