Nelson Mandela's wife has said the 94-year-old icon is "fine" and his health is improving after he was hospitalised more than a week ago for pneumonia, a report said Friday.

"Madiba is fine, Madiba is getting better and better," said Graca Machel late Thursday, referring to 94-year-old Mandela's clan name, the private eNCA news channel reported.

"He is in hospital simply because the doctors want to be absolutely sure that he is strong enough to go home and nothing is going to recur."

Her comments marked the latest upbeat update on the country's first black president, who was hospitalised shortly before midnight on March 27.

The admission was his third hospital stint since December.

On Thursday, President Jacob Zuma said that he had visited his predecessor and that doctors had said he was showing continuous improvement.

"Madiba is stable and we are thankful that he is responding well to treatment and that he is much better," Zuma said,

To help him breathe without difficulty, doctors last week drained excess fluid that had built up on the lining of his lungs.

Last month Mandela spent a night in hospital for a scheduled check-up and in December he was admitted for 18 days for a lung infection and gallstones surgery, his longest hospital stay since he walked free from 27 years in jail in 1990.

Mandela's latest health scare has sparked an outpouring of wishes and prayers from across the globe and at home.

"Thank you very very very much for lifting him up. God is listening," said Machel.

No indication has been made as to when Mandela could be released from hospital, with his grandson also saying this was likely only when doctors were satisfied.

"We are always very concerned when he goes into hospital," his grandson Mandla Mandela told SABC public television on Thursday.

But he noted that Mandela had undergone several "scheduled hospital visits" for check-ups and monitoring in recent months and said his grandfather was in the "good capable hands" of his doctors.

"We are sure that in no time when the doctors are fully satisfied with the investigations they are doing they will be sending him back home," he added.

Mandela's lung problems date back to his 27 years in apartheid jail when he was diagnosed with early-stage tuberculosis in 1988.

He has also been treated for prostate cancer and has suffered from stomach ailments.