Pretoria, South Africa (CNN) -- Authorities increased security around a Pretoria hospital where former South African leader Nelson Mandela remained in intensive care, three days after being rushed there with a recurring lung infection.
Police set up gates and fences around entrances to the facility Tuesday, closely checking vehicles trying to gain access.
The increasingly frail Mandela was taken to a hospital in Pretoria on Saturday. Later in the day, the South African president's office said the 94-year-old former leader was in a "serious but stable condition."
He was breathing on his own and his wife was by his side, the office said at the time.
The government said Tuesday that Mandela's condition remained unchanged. President Jacob Zuma visited Mandela late Monday and was satisfied with the medical care he was receiving.
"Yesterday I met the team of doctors who are treating him," Zuma told a reporter. "They gave me a very thorough briefing and really I was very confident that they know what they are doing and they are doing a good job. Whilst it is very serious, he is stabilized. And we are all praying for him to recuperate quickly."
Meanwhile, Mandela's daughter Zenani Dlamini, who is the South African ambassador to Argentina, has flown back to South Africa to be with her father.
African National Congress lawmaker and Mandela's ex-wife, Winnie, also visited him Monday.
Mandela has been in and out of hospitals in recent years. Each episode has sparked renewed concerns.
His history of lung problems dates to when he was a political prisoner on Robben Island during the apartheid era, and he has battled respiratory infections over the years.
He has not appeared in public since South Africa hosted the World Cup in 2010.
Last year, he spent the Christmas holidays undergoing treatment for a lung infection and gallstones, one of his longest hospital stays since his release from prison in 1990.