Former South African President Nelson Mandela was hospitalized overnight for routine medical tests, reviving concern over the health of the frail 92-year-old anti-apartheid icon.
Mandela was admitted to a Johannesburg hospital on Wednesday for what his foundation described as routine tests, but Talk Radio 702 reported that he had been seen by a specialist pulmonologist, who treats respiratory systems.
President Jacob Zuma and the ruling African National Congress appealed for calm on Thursday after the hospitalization set off considerable speculation in local media about Mandela's health.
"President Mandela is comfortable and is well looked after by a good team of medical specialists," Zuma said in a statement. The ANC said there was no reason to panic.
"He is a 92-year-old and will have ailments associated with his age, and the fact that he stayed the night should not suggest the worst," ANC spokesman Jackson Mthembu said.
Mandela was likely to stay in hospital for a few more days, local media reported.
Mandela has not been seen in public since the soccer World Cup final in July last year.
Police were called in to control traffic at the Milpark Hospital in a leafy Johannesburg suburb as scores of journalists, photographers and television crews converged on it.
Several members of Mandela's family, including his wife Graca Machel, visited the hospital after his admission, Reuters witnesses said.
Mandela retired from public life in June 2004 before his 86th birthday, telling his adoring compatriots: "Don't call me, I'll call you."
Since then he has rarely appeared in public and when he did, he appeared increasingly frail. In addition to the World Cup, Mandela appeared at a couple of ANC rallies before general elections in 2009.
Mandela was treated in the 1980s for tuberculosis and later had an operation to repair damage to his eyes. In 2001 he had treatment for prostate cancer.
South African Nobel Peace Prize laureate Desmond Tutu said this week he had met Mandela last week. "He was all right, I mean, he's 92, you know. And he's frail."
"What more do we want from him? We want him to remain forever, but you know... anything can happen," Tutu told reporters in Bloemfontein on Thursday, the Sapa news agency reported.
Mandela -- known by his clan name of Madiba in South Africa -- has been on holiday with his wife, local media reported.
Earlier this month the ANC said it wanted Twitter to take action after a hoax report of Mandela's death was widely distributed on the social network site.
The Nelson Mandela Foundation declined to comment on his health on Thursday but said in an earlier statement: "He is in no danger and is in good spirits." According to Internet website Trendistic, which tracks Twitter trends, use of the word "Mandela" has increased sharply over the past 24 hours. http://trendistic.com/mandela/_24-hours
South Africans also used social network site Facebook to post their concern. "All the best for you! hope (your) dad is just fine!" wrote one person on the Facebook page of Mandela's daughter, Zinzi.