"President Jacob Zuma last night, June 10, met with the medical team that is treating former (South African) President Nelson Mandela, and they gave him a thorough briefing. The former President is still in a serious, but stable condition in a Pretoria hospital," a presidential statement said on Tuesday.
"President Zuma has full confidence in the medical team, and is satisfied that they are doing their best to make Madiba (Mandela's clan name) better," it said.
"He is receiving intensive care treatment," presidential spokesman Mac Maharaj was quoted by media reports as saying.
Mandela was shifted to Mediclinic Heart Hospital in Pretoria in the early hours on Saturday, the fourth time since December he has been admitted.
The President's office had said on Saturday that Mandela was in a "serious but stable condition."
He was breathing on his own and his wife was by his side, the Presidency had said at the time.
Security was beefed up at the hospital with police on Tuesday setting up gates and fences around entrances to the facility, closely checking vehicles trying to access the compound.
In April, doctors diagnosed Mr. 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 in July 2013.
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 him on Monday.
"I've seen my father and he's well. He's a fighter," 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.