* Government says he suffering recurrence of previous infection
* Former president's "sparkle" is fading, wife Graca says
* Famed anti-apartheid leader is hero to South Africans
JOHANNESBURG, Dec 11 (Reuters) - Former South African President Nelson Mandela, who is 94 and has been in hospital since Saturday for tests, has suffered a recurrence of a lung infection but is responding to treatment, the government said on Tuesday.
The revered anti-apartheid leader and Nobel Peace laureate is spending his fourth day in a hospital in the South African capital Pretoria. He remains a hero to many of South Africa's 52 million people and two brief stretches in hospital in the last two years made front page news.
"Doctors have concluded the tests, and these have revealed a recurrence of a previous lung infection, for which Madiba is receiving appropriate treatment and he is responding to the treatment," the government said in a statement.
Mandela, whose clan name is 'Madiba', was admitted to the Pretoria military hospital on Saturday after being flown from his home village of Qunu, which is in a remote, rural part of the Eastern Cape province.
Until now, South African authorities had given few details about the reason for his latest visit to hospital.
In an interview late on Monday with South Africa's eNCA television channel, Mandela's Mozambican-born wife Graca said the former president's "sparkle" was fading.
When he was admitted to hospital on Saturday, officials stressed there was no cause for concern although domestic media reports suggested senior members of the government and people close to him had been caught unawares.
Mandela, South Africa's first black president and a global symbol of resistance to racism and injustice, spent 27 years in apartheid prisons, including 18 years on the windswept Robben Island off the coast of Cape Town.
He was released in 1990 and went on to be elected president in the historic all-race elections in 1994 that ended white-minority rule in Africa's most important economy.
He used his unparalleled prestige to push for reconciliation between whites and blacks, setting up a commission to probe crimes committed by both sides in the anti-apartheid struggle.
Mandela's African National Congress has continued to govern since his retirement from politics in 1999, but has been criticised for perceived corruption and slowness in addressing apartheid-era inequalities in housing, education and healthcare.
Mandela spent time in a Johannesburg hospital in 2011 with a respiratory condition, and again in February this year because of abdominal pains. He was released the following day after a keyhole examination showed there was nothing serious.
He has since spent most of his time in Qunu.
His fragile health prevents him from making any public appearances in South Africa, although he has continued to receive high-profile domestic and international visitors, including former U.S. President Bill Clinton in July.