Johannesburg: Nelson Mandela spent a fourth day in intensive care and continued to be in a "serious but stable" condition. (Agencies)
Security was beefed up at the hospital where 94-year-old anti-apartheid icon and former South African President is battling a recurrent lung infection.
"Former President Nelson Mandela remains in hospital, and his condition is unchanged," the presidency said in a brief statement on the health of the revered Nobel laureate.
"He is receiving intensive care treatment," presidential spokesman Mac Maharaj said.
Mandela was shifted to Mediclinic Heart Hospital in Pretoria in the early hours on Saturday.
Police on Tuesday set up gates and fences around entrances to the facility, closely checking vehicles trying to access the compound.
In April, doctors diagnosed Mandela with pneumonia and drained fluid from his chest. South Africans offered prayers at church services on Sunday for the ailing leader, who will turn 95 next month. Hundreds of worshippers attended Mass at Soweto's Regina Mundi church, famous for its role in the anti-apartheid campaign.
Mandela's wife, Graca Machel, cancelled a scheduled appearance in London on Saturday to remain at her husband's bedside. Relatives, including his ex-wife Winnie Madikizela-Mandela and their daughter Zindzi visited the ailing former leader yesterday.
"I've seen my father and he's well. He's a fighter," one of Mandela's daughters Zindzi said. Mandela served as president from 1994 to 1999. He was previously imprisoned for 27 years, and is believed to have suffered damaged lungs while working in a prison quarry.
He contracted tuberculosis in the 1980s while being held in jail on the windswept Robben Island. Though Mandela retired from public life in 2004 and has been rarely seen in public since 2010, he remains a towering symbol in South African public life.
Johannesburg: Nelson Mandela spent a fourth day in intensive care and continued to be in a "serious but stable" condition.