Nelson Mandela’s condition has deteriorated to “critical,” the South African government said Sunday night, nearly three weeks after the former South African leader and anti-apartheid icon was hospitalized with a recurring lung infection.

The office of South African President Jacob Zuma said that he and ruling African National Congress deputy president Cyril Ramaphosa visited Mandela, 94, on Sunday evening and that doctors informed them that Mandela’s condition had turned critical in the past 24 hours.

“The doctors are doing everything possible to get his condition to improve and are ensuring that Madiba is well-looked after and is comfortable,” Zuma said in an e-mailed statement, referring to Mandela by his clan name. “He is in good hands.”

For the past 17 days, Mandela has been receiving care at a medical facility in Pretoria, the South African capital— the fourth time he has been hospitalized since December. But there was little indication that his condition had become critical. As of Saturday, the South African government had characterized his condition as “serious but stable.”

The apartheid regime imprisoned Mandela for 27 years, releasing him in 1990. He became the nation’s first black president following South Africa’s first multiracial elections in 1994, won by the African National Congress. Mandela has not been seen in public since the World Cup soccer tournament was held in South Africa in 2010.

Over the weekend, the government came under fire following reports that an ambulance transporting Mandela to the hospital on June 8 broke down, and that Mandela had suffered cardiac arrest. Another ambulance arrived to take Mandela to Pretoria, about a 45 minute drive from Mandela’s home in an upscale Johannesburg neighborhood.

In his statement, Zuma confirmed the incident but said that doctors dismissed the media reports of the cardiac arrest, adding that there “is no truth at all in that report.”

“There were seven doctors in the convoy who were in full control of the situation throughout the period. He had expert medical care,” Zuma said. “The fully equipped military ICU ambulance had a full complement of specialist medical staff including intensive care specialists and ICU nurses.”