Former South African President and anti-apartheid icon Nelson Mandela underwent a successful surgery to remove gallstones and is recovering well, a Presidential spokesperson said today.

"This morning (Saturday) the former president underwent a procedure via endoscopy to have the gallstones removed," President Jacob Zuma's spokesman Mac Maharaj said in a statement.

The 94-year-old leader was hospitalised in Pretoria on December 8 for a lung infection.

"The procedure was successful and Madiba is recovering. The medical team decided to attend to a lung infection before determining when to attend to the gallstones."

The statement followed a week of speculation about Mandela's health and a silence on his condition from both government and his family.

However, there was no indication of when Mandela would return home.

Mandela was admitted to a hospital widely believed to have been 1 Military Hospital, since the military assumes responsibility for the health of heads of state, including retired ones.

Maharaj had earlier said that Mandela was being treated for a recurring lung condition.

Mandela had contracted tuberculosis during his 27 years of imprisonment as a political prisoner.

Mandela's latest hospital stay is the second longest of several health scares in recent years after he underwent seven weeks of radiotherapy for prostate cancer in 2011.