Former President Nelson Mandela of South Africa is in hospital for the second time in just over a year. He was admitted on Saturday.
Government officials said he needed "specialist attention" for a "long-standing abdominal complaint".
A statement from President Jacob Zuma's office asked for his family to be given privacy.
The BBC reports the statement did not say which hospital Mr Mandela was admitted to, but there are suggestions it was a military hospital in the capital, Pretoria.
Mr Mandela, 93, returned to Johannesburg last month from his rural home in the Eastern Cape. He received treatment in the Milpark hospital for a serious chest infection in January last year.
Mr Mandela retired from public life eight years ago - his last public appearance was at the World Cup in South Africa in 2010.
The Nobel Peace Prize winner is affectionately known in South Africa as by his clan name, Madiba.
He spent 27 years in prison for his fight against white minority rule before being released in 1990.
In 1994, he became South Africa's first black president, stepping down in 1999 after one term.