Former South African president Nelson Mandela was admitted to hospital on Saturday for a "routine test", his second period of hospital treatment in less than three months, the government said.
A spokesman for President Jacob Zuma said there was "no need for panic" and that doctors were treating Mandela for a pre-existing condition consistent with his age.
It did not reveal any more details about the condition of the 94-year-old anti-apartheid leader, other than to say he was in a hospital in the capital, Pretoria.
The tone of the government's announcement was in keeping with previous announcements about Mandela's health.
Mandela, South Africa's first black president, spent nearly three weeks in hospital in December with a lung infection and after surgery to remove gallstones. It was his longest stay in hospital since his release from prison in 1990.
Since his release on December 26 he had been receiving treatment at his Johannesburg home.
The Nobel Peace Prize laureate has a history of lung problems dating back to when he contracted tuberculosis as a political prisoner. He spent 27 years in prison, including 18 years on the windswept Robben Island off Cape Town.
He became president of Africa's biggest economy in 1994 after the first all-race elections brought an end to white-minority apartheid rule.
Although he is deeply revered by nearly all of South Africa's 50 million people, he has played no part in public life for the last decade.