The revered anti-apartheid leader was admitted Saturday to a Pretoria hospital and is being treated for a lung infection, the South African government's news agency said Wednesday.
Hospital officials said a large number of well-wishers have camped in front of the hospital since news of Mandela's illness surfaced.
"We continue to request that [Mandela] and his family be accorded the necessary space and privacy and thank the media and the public for cooperation," the country's presidential office said.
In February, Mandela, the South Africa's first black president, was hospitalized for tests to address a chronic stomach complaint, the government said at the time. In January 2011, he was hospitalized for an acute respiratory infection.
Mandela, 94, retired from public life years ago, and was last seen publicly during the World Cup soccer tournament held in South Africa in 2010.