Nelson Mandela is "responding positively" to treatment after being re-admitted to hospital with a lung infection, the latest health scare for the much-loved anti-apartheid icon.
The frail 94-year-old former South African president was hospitalised just before midnight on Wednesday, the presidency said, urging people around the world to pray for him.
"The doctors advise that former president Nelson Mandela is responding positively to the treatment he is undergoing for a recurring lung infection," President Jacob Zuma's office said in a short statement on Thursday.
"He remains under treatment and observation in hospital."
The Nobel peace laureate, regarded as the father of the "rainbow nation", was conscious when he was admitted, presidency spokesman Mac Maharaj told AFP.
It is the second time this month that Mandela has spent the night in hospital and follows a nearly three-week stay in December for the lung infection and for gallstone surgery, after which he was released for home-based care.
Mandela was diagnosed with early-stage tuberculosis in 1988 during his nearly three decades in prison under the white minority apartheid regime and has long problems with his lungs.
"Doctors are attending to him, ensuring that he has the best possible expert medical treatment and comfort,'' Zuma's office said earlier.
Zuma wished "Madiba", as South Africa's first black president is affectionately known, a quick recovery and asked for people around the world to pray for him.
Revered at home and abroad as the symbol of the country's peaceful shift to democracy after apartheid, his ``long walk to freedom'' in 1990 after 27 years behind bars was one of the most potent images of the time.
But as he has grown increasingly frail, he has not appeared in public since South Africa's World Cup soccer final in 2010, six years after retiring from public life.