South Africa's former president Nelson Mandela has been admitted to a hospital in Pretoria "to undergo tests", the Presidency said on Saturday.

"President Jacob Zuma wishes to advise that former President Nelson Mandela has today, 8 December 2012, been admitted in hospital in Pretoria to undergo tests," presidential spokesman Mac Maharaj said in a statement.

But Maharaj said Mandela was receiving routine medical checkup as he has always done so in the past.

"As said before, former President Mandela will receive medical attention from time to time which is consistent with his age,"

Maharaj said Zuma wants to assure the public that there was no cause for alarm as Mandela was doing well.

"We wish Madiba (nickname for Mandeal) all the best. The medical team is assured of our support as they look after and ensure the comfort of our beloved founding President of a free and democratic South Africa."

The Presidency appealed to the media and the public to respect the privacy of Mandela and his family.

Mandela turned 94 on July 18 this year. His health has been a focus of concern.

Zuma paid a visit to Mandela at his rural home in Qunu village in Eastern Cape Province in July, days before his 94th birthday. The president said at that time Mandela was in good health.

Mandela, who was imprisoned for 27 years during apartheid, was elected the country's first black president in 1994.