Nelson Mandela is "comfortable", the South African government has said after the anti-apartheid icon spent the night in a Pretoria hospital, and underwent medical tests described as "consistent with his age".

President Jacob Zuma on Sunday visited the country's 94-year-old first black president who was hospitalised a day earlier and said he "found him comfortable, and in good care".

The iconic leader was admitted on Saturday for what Zuma's spokesman and former Mandela prison inmate Mac Maharaj said was for tests and medical attention consistent with the nanogenarian's age.

It was the second time the 94-year-old and increasingly frail Mandela was hospitalised this year and officials have moved to allay fears around his health.

'No cause for alarm'

The South African government said he was doing well shortly after he was taken in for "normal" tests "consistent with his age" and insisted there was "no cause for alarm".

Speaking to Al Jazeera, Mac Maharaj said: "Mandela will receive medical attention from time to time which is consistent with his age."

Keith Khoza spokesman of the ruling African National Congress party, which Mandela once led, said "he is in perfect health, everything is well, it's just that he has to undergo these regular check ups".

Officials have refused to give more details about his condition and the tests he is taking.

Mandela, who became South Africa's first black president after the country's first all-race elections in 1994, was admitted to hospital in February as well because of abdominal pain but released the following day after a keyhole examination showed there was nothing seriously wrong with him.

He has since spent most of his time in his ancestral home in Qunu, a village in the impoverished Eastern Cape province.

His frail health prevents him from making any public appearances in South Africa, although in the last few months he has continued to receive prominent visitors, including former US President Bill Clinton.

Source: Al Jazeera and agencies