Former South African president Nelson Mandela has suffered a recurrence of a lung infection but is responding to treatment, the government has said.

The revered anti-apartheid leader and Nobel Peace laureate is spending his fourth day in hospital in the capital, Pretoria.

Known affectionately by his clan name "Madiba", Mr Mandela remains a hero to many of South Africa's 52 million people.

Mr Mandela was admitted to the Pretoria military hospital on Saturday after being flown from his home village of Qunu, in a remote part of the Eastern Cape province.

Until now, authorities had given few details about the reason for his latest visit to hospital.

In an interview broadcast on South Africa's eNCA television channel, Mr Mandela's Mozambican-born wife Graca said the former president's "sparkle" was fading.

When he was admitted to hospital at the weekend, officials stressed there was no cause for concern.