The South African government says former president Nelson Mandela remains in a critically-ill condition in hospital on Monday.
Mr Mandela is in a Pretoria hospital with a recurring respiratory infection. The government said doctors were doing everything they could for the 94-year-old anti-apartheid hero.
Mr Mandela was rushed to hospital in the early hours of 8 June. Until Sunday, official communiques had described his condition has "serious but stable", although comments last week from Mandela family members and his presidential successor, Thabo Mbeki, suggested that he was on the mend.
President Jacob Zuma and deputy leader of the ruling African National Congress Cyril Ramaphosa visited Mr Mandela in hospital on Sunday where doctors said his condition had worsened in 24 hours.
At a news conference on Monday morning (local time), Mr Zuma said he could not give any more medical details and urged the country to pray for Mr Mandela.
"All of us in the country should accept the fact that Madiba [Mr Mandela's clan name] is now old. As he ages, his health will ... trouble him and I think what we need to do as a country is to pray for him."
Presidential spokesperson Mac Maharaj spoke of the need to be sombre about the news and not hold out false hopes.
It is the fourth hospital stay since December last year for the former president, who has a history of lung problems dating back to his time at the Robben Island prison camp near Cape Town.
His condition is bound to concern South Africa's 53 million people, for whom Nelson Mandela remains the architect of a peaceful transition to democracy after three centuries of white domination, Reuters reports.
In February 1990, he was released from jail and after the country's first democratic elections became South Africa's first black president in 1994, serving for five years.
Since stepping down in 1999 after one term in office he has played little role in public life. His last public appearance was at the final of the soccer World Cup in Johannesburg's Soccer City stadium in July 2010.
Mr Mandela is due to celebrate his 95th birthday on 18 July. The public's last glimpse of him was a brief clip aired by state television in April this year during a visit to his home by Mr Zuma and other senior ANC officials.