US news channel CNN late on Wednesday night reported that an official "who had been briefed in detail on [Nelson Mandela's] condition" revealed that the former president was on life support.
Presidency spokesperson Mac Maharaj would not confirm or deny the report to the Mail & Guardian.
"I can't comment on that. What I can repeat is that, based on doctor's advice, we have been informed that Mr Mandela's situation has turned critical, and it remains critical. And we have explained that we don't go into any of the clinical details," Maharaj said.
He reiterated that doing so would be breaking doctor-patient confidentiality.
"We appeal to the media that they should not become party to the breaking of that ethical rule," Maharaj said.
On Monday, President Jacob Zuma held a briefing attended by editors during which Maharaj lambasted journalists for their questioning of doctors around Madiba's health.
Along with allegations of life support, the Citizen reported on Wednesday that Mandela was also suffering from kidney failure and was undergoing dialysis for three hours every second day.
Meanwhile, reports on Tuesday said elders at the Qunu community, where Mandela is from, were briefed on news about Mandela.
But family friend Bantu Holomisa stressed that the meeting did not reveal any more details about the former statesman's condition.
On Sunday, the presidency broke the news that the former president was critically ill after being in hospital with a recurring lung infection since June 8.
Meanwhile, Eyewitness News tweeted on Wednesday night that President Jacob Zuma was photographed leaving the hospital in Pretoria where Mandela is admitted.
#Madiba President Jacob Zuma has just been photographed leaving the hospital here in Pretoria before being followed by his convoy. RDT
— EWN Reporter (@ewnreporter) June 26, 2013