Former South African president and anti-apartheid leader Nelson Mandela remained in a "serious but stable" condition in a Pretoria hospital on Tuesday after four days of treatment for a lung infection, the government said.
Speaking to the national broadcaster, President Jacob Zuma said he had been updated by doctors on the health of the 94-year-old Mandela, who became South Africa's first black president after historic all-race elections in 1994.
"I met a team of doctors who are treating him. They gave me a thorough briefing. They are doing a very good job," Zuma told the South African Broadcasting Corporation.
"Knowing him as I do, he is a good fighter, he will be with us soon," said Zuma, who was imprisoned on Robben Island with Mandela for 10 of his 27 years.
Police tightened security around Pretoria's Medi-Clinic Heart Hospital which is treating Mandela, revered around the world for leading the struggle to end South Africa's apartheid system of racial segregation and white-minority rule.
Around a dozen police officers were deployed outside the building, which was cordoned off by barriers and police tape to keep a phalanx of domestic and international reporters and television crews away from the entrance.
All vehicles going into the building were being searched.
Mandela was admitted in the early hours of Saturday with a recurring lung infection. The hospital stay is his fourth since December, and there is a growing realisation among South Africa's 53 million people that they will one day have to say goodbye to the father of the "Rainbow Nation" that Mandela tried to forge from the ashes of apartheid.
Mandela has received visits from family members including his current and former wives, Graca Machel and Winnie Madikizela-Mandela.
Mandela has a history of lung problems dating back to his time on the wind-swept Robben Island prison camp near Cape Town. Before his 1990 release he spent nearly three decades in prison for conspiring to overthrow the apartheid government.