Former South African president and anti-apartheid hero Nelson Mandela was in a "serious but stable" condition on Saturday after being taken to hospital with a recurrence of a lung infection, the government said.
The 94-year-old, who became the first black leader of Africa's biggest economy in 1994 after historic all-race elections, has been in hospital three times since December. He has been battling the infection for several days, a statement said.
"This morning at about 1:30 a.m. (2330 GMT) his condition deteriorated and he was transferred to a Pretoria hospital. He remains in a serious but stable condition," the government said.
Presidential spokesman Mac Maharaj told local television that "doctors have assured us he is comfortable".
However, the government's choice of words, in particular the use of "serious", is clear cause for concern to South Africa's 53 million people, for whom Mandela remains a potent symbol of the struggle against decades of white-minority rule.
"It's such painful news but I pray for him that he can get better and better and better as he is the best man in this country," said Pretoria resident Khodani Mulwena.
The Nobel Peace Prize laureate stepped down as president in 1999 after one term in office and has been removed from politics for a decade. His last appearance in public was at the final of the soccer World Cup in Johannesburg in 2010.
He appeared in a brief television clip aired by state television in April during a visit to his home by President Jacob Zuma.
At the time, the ruling African National Congress (ANC) assured the public Mandela was "in good shape", although the footage showed a thin and frail old man sitting expressionless in an armchair with his head propped against a pillow.
'Too Much a Saint'
Since his withdrawal from public life, he has divided his time between his plush Johannesburg home and Qunu, the village in the impoverished Eastern Cape where he was born and spent his early years.
Mandela spent nearly three weeks in hospital in December with a lung infection and after surgery to remove gallstones.
That was his longest stay in hospital since his release from prison in 1990 after serving almost three decades behind bars or on the Robben Island prison camp near Cape Town for conspiring to overthrow the apartheid government.
His history of lung problems dates back to his years on Robben Island, where he contracted tuberculosis.
Although he remains widely revered, Mandela is not without detractors at home and in the rest of Africa who feel he made too many concessions to whites, who make up just 10 percent of the population, in the post-apartheid settlement.
Despite more than 10 years of affirmative action policies aimed at redressing the balance, South Africa remains one of the world's most unequal societies with whites still controlling much of the economy.
On average a white household earns six times more than a black one.
"Mandela has gone a bit too far in doing good to the non-black communities, really in some cases at the expense of (blacks)," Zimbabwean President Robert Mugabe, 89, said in a documentary aired on South African television this month.
"That's being too saintly, too good, too much of a saint."