Anti-apartheid icon and former South African President Nelson Mandela has spent a night in hospital after being admitted for a "scheduled medical check-up", less than three months after being treated for a lung infection and gallstones.

"There isn't an update. I just have to allow the doctors to advise me," presidential spokesman Mac Maharaj said a day after the 94-year-old leader was admitted to the hospital.

"Former president Nelson Mandela was admitted to hospital in Pretoria on March 9 for a scheduled medical check-up to manage the existing conditions in line with his age," presidential spokesman said in a statement.