CAPE TOWN - South Africa's ailing ex-president Nelson Mandela managed to sit up, a sign of great improvement in his condition, his daughter Zindzi Mandela said on Friday.

"He's fine, Tata (father) now manages to sit up, like now he sits up in a chair for a few minutes in a day, every day you know he becomes more alert more responsive," Zindzi said in remarks published by the South African Broadcasting Corporation (SABC).

"Tata is determined not to go anywhere anytime soon, I cannot stress this enough. People must stop saying to the family let go let go, we are just looking at this man who is saying I'm not going anywhere," said Zindzi.

Zindzi said her father has a strong constitution, will and strength which keeps him alive.

"You know he just doesn't have the strength of a man, he just has the strength that is beyond anything that can be explained. Because even now with the challenges to his health, he somehow manages to bounce back when everyone assumes this is the end," said Zindzi.

The 95-year-old anti-apartheid icon has been in hospital for two months, receiving treatment for a recurring lung infection. He was admitted to hospital on June 8.

On Thursday, Mandela's ex-wife Winnie Madikizela-Mandela said Mandela was now breathing normally.

Winnie denied reports that Mandela was in a permanent vegetative state, saying there was no need to conceal the fact.

Mandela's eyes still "lit up" when his children came to visit him, Winnie told the British Sky News. "That is how he communicates with them."

Winnie said the medical team has done a good job in ensuring that Mandela remains "comfortable."