Nelson Mandela at a state celebration for his 90th birthday.
The now-94-year-old former South African president was admitted to a military hospital three days ago for medical tests.
The government said the anti-apartheid leader's condition was comfortable.
It provided no other details of the health of the country's first black president, who came to power after historic all-race elections in 1994.
Mandela is a hero to many South Africans and two brief stays in hospital in the last two years have made front page news.
(SOUNDBITE) (English) LOCAL RESIDENT, TSHIDI MODIPANE SAYING
"I hope that he recovers soon and, yeah, health is important, and we hope that he will recover soon."
(SOUNDBITE) (English) LOCAL RESIDENT, JOHN MATJELE SAYING:
"I wish him all the best and a speedy recovery."
Mandela's frail health prevents him from making any public appearances in South Africa, although he has continued to receive high-profile domestic and international visitors including former U.S. President Bill Clinton.