Nelson Mandela remained hospitalised in a critical state for a fourth week Saturday after doctors ruled out turning off his life support unless he suffered massive organ failure.

Meanwhile his grandson's lawyers were planning to lodge an official complaint over a court document which they say falsely claimed he was "in a permanent vegetative state".

The anti-apartheid hero's health condition was unchanged over the weekend, South Africa's presidential spokesman Mac Maharaj told AFP.

He is in a critical but stable condition after his June 8 admittance for an obstinate pulmonary infection and relies on machines to help him breathe.

A close friend of the former statesman had said 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," Denis Goldberg, who has known Mandela for over 50 years, told AFP on Friday.

"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 10 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 said that is not the case, but refused to give further details of his condition, citing the need to respect Mandela's privacy.

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

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 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.

Meanwhile an acerbic feud between his relatives showed little sign of abating.

Lawyers for his grandson Mandla would lodge a formal complaint against his relatives' legal team who they claim gave a false version of Nelson Mandela's health.

"They relied on certain affidavits in particular with regards to the health of the (former) president which wasn't true," Mandla's lawyer Gary Jansen told Sapa news agency.

The statesman's three deceased children were buried at his proposed burial ground in Qunu, his childhood village, on Thursday.

Fifteen family members had won a court order against Mandla after he moved the graves two year ago without their consent.

But the fall-out from the dispute continued to reverberate.

In nationally-televised news conference Mandla accused one of his brothers of impregnating his wife and said others were born out of wedlock.

The family had laid a charge of grave tampering against him, and investigators were wrapping up the case, a spokesman told AFP.

"The police are finalising the investigation and the docket will be handed over to the senior prosecutor for his decision on Tuesday," said police spokesman Mzukisi Fatyela.

Leading South Africans urged Mandela's family to end their increasingly acerbic feud over the gravesites.

South African Nobel peace laureate Desmond Tutu pleaded with them 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.

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