A spokesman for the South African Presidency has said that earlier media reports that former president Nelson Mandela has been discharged from hospital were "incorrect".
Mac Maharaj said: "Madiba is still in hospital in Pretoria, and remains in a critical but stable condition.
"At times his condition becomes unstable, but he responds to medical interventions."
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The Prime Minister has praised the former soldier's "huge professionalism" in trying to save the life of Pc Keith Palmer.
The man who carried out the Westminster attack is thought to be British born and was once investigated by MI5, the Prime Minister has said.
Jason Day, who lost his father to stomach cancer at the age of 12, broke down in tears as he explained his shock exit during the WGC event.