Nelson Mandela has "recovered" from recent surgery and a lung infection for which the 94-year-old spent nearly three weeks in hospital, the presidency said Sunday, citing his doctors.

He "has recovered from his surgical procedure and the lung infection, his doctors said today," said a statement from President Jacob Zuma's office.

"The medical (examination) said president Mandela has made steady progress and that clinically, he continues to improve," it said.

"He had undergone an operation to remove gallstones last month and was also troubled by a recurring lung infection. He continues to receive high care at his Houghton (Johannesburg) home and his daily routine is being gradually re-established."

On Thursday, Mandela's grandson Mandla Mandela told AFP that the former South African president "is healed and is stronger than before".

The revered former statesman was flown to a Pretoria hospital on December 8 from his childhood home in Qunu.

Mandela was discharged from hospital more than a week ago after his longest stay in hospital since being released from prison in 1990.