Nelson Mandela's doctors have rejected the idea of turning off the ailing icon's life support unless he suffers massive organ failure, a close family friend told AFP Friday.

Denis Goldberg -- an anti-apartheid activist who has been Mandela's friend for more than half a century -- said the issue of turning off life support was discussed and ultimately dismissed.

"I was told the matter had been raised and the doctors said they would only consider such a situation if there was a genuine state of organ failure," Goldberg said.

"Since that hasn't occurred they were quite prepared to go on stabilising him until he recovers."

The 80-year-old Goldberg was convicted along with Mandela in 1964 for their fight against white-minority rule.

He visited the former president in hospital on Monday.

A court document filed by a lawyer for Mandela's family nine days ago stated the 94-year-old was "assisted in breathing by a life support machine."

"The Mandela family have been advised by the medical practitioners that his life support machine should be switched off," the court filing read.

"Rather than prolonging his suffering, the Mandela family is exploring this option as a very real probability."

The document - which was designed to press a court to urgently settle a family row over the remains of Mandela's children -- also stated that Mandela was "in a permanent vegetative state."

South Africa's presidency has stated that is not now the case, but has refused to give further details of his condition, citing the need to respect Mandela's privacy.

On the day the document was drafted, President Jacob Zuma abruptly cancelled a trip to Mozambique to confer with Mandela's doctors amid fears the 94-year-old may be close to the end.

Zuma, Mandela family members and his close friends have since reported his condition has improved.

South African presidential spokesman Mac Maharaj told AFP on Friday that Zuma's office "had not been party" to the court material and would not speculate on its content.

"We did not file any document and we are not saying that it's true or not true," he said.

Earlier Goldberg said Mandela was "clearly a very ill man, but he was conscious and he tried to move his mouth and eyes when I talked to him."

"He is definitely not unconscious," he added, saying "he was aware of who I was".

Mandela, who spent 27 years in prison for fighting white-minority rule and went on to lead the process of racial reconciliation as South Africa's first black president, has now spent a month in hospital after being admitted with a recurrent lung infection.

South Africa's parliament on Friday hosted a prayer service in a Cape Town cathedral where Mandela was hailed as "an icon of a truly free South Africa".

"It is a reflective period for our people," said national assembly deputy speaker NomaIndiya Mfeketo.

"The thought of Madiba in hospital indisposed due to illness is harrowing. This is not what we wish for our beloved hero."

Meanwhile leading South Africans urged Mandela's family to end an increasingly acerbic family feud over the gravesites of three of Mandela's children.

On Thursday Mandela's grandson Mandla launched a tirade at close family members who took him to court to force him to reinter Mandela's children at the revered former South African leader's proposed burial ground in Qunu, his childhood village.

Mandla accused one of his brothers of impregnating his wife and said others were born out of wedlock.

The three bodies were reburied Thursday in Qunu, but the fall-out from the dispute continued to reverberate.

South African Nobel peace laureate Desmond Tutu pleaded with Mandela's family not to "besmirch" the former president's name.

"Please, please, please may we think not only of ourselves. It's like spitting in Madiba's face," said Tutu in a statement, using Mandela's clan name.

Presidential spokesman Maharaj also urged the family to solve the increasingly bitter dispute "amicably".

"It is regrettable that there is a dispute going on amongst family members and we'd like that dispute to be resolved as amicably and as soon as possible," he said.

Mandela was rushed to hospital on June 8 with a recurring respiratory infection.