Former President Nelson Mandela has been released from hospital after an overnight stay for minor diagnostic surgery to determine the cause of an abdominal complaint, a spokesman for the country's current leader said.

Spokesman Mac Maharaj said the 93-year-old Nobel peace laureate had undergone a laparoscopy, a procedure that involves surgeons making an incision in the stomach area to insert a thin, lighted tube to look at abdominal organs.

"The doctors have decided to send him home as the diagnostic procedure he underwent did not indicate anything seriously wrong with him," President Jacob Zuma's office added in a statement.

Officials had not disclosed where he was being treated to protect his privacy.

Earlier in the day, Mr Zuma had released a statement saying that Mr Mandela was "surrounded by his family and is relaxed and comfortable".

"The doctors are happy with the progress he is making. We thank all South Africans for their love and support of Madiba. We also thank all for affording Madiba and his family privacy and dignity," said Mr Zuma, referring to Mr Mandela by his clan name.

Mr Mandela, who spent 27 years in prison for fighting racist white rule, became South Africa's first black president in 1994 and served one five-year term. He now is officially retired, and last appeared in public in July 2010.

On Sunday, well-wishers prayed for Mr Mandela at Regina Mundi church in Soweto, a former centre of anti-apartheid protests and funerals.

In 1997, Mr Mandela spoke at the church, calling it a "battlefield between forces of democracy and those who did not hesitate to violate a place of religion with tear gas, dogs and guns."