Cape Town — Former President Nelson Mandela's condition has become "critical", the office of South African President Jacob Zuma has announced.

In a statement released late Sunday night, South African time, Zuma's office said he and the deputy president of the ruling African National Congress, Cyril Ramaphosa, had visited Mandela in hospital earlier in the evening.

"They were briefed by the medical team who informed them that the former president's condition had become critical over the past 24 hours," the statement said. They also met and discussed Mandela's condition with his wife, Graca Machel, at the hospital.

Zuma spokesman Mac Maharaj declined to discuss the detail of Mandela's condition on grounds of respecting "the ethical issues of doctor/patient confidentiality, privacy and human dignity."

Zuma was quoted as saying "the doctors are doing everything possible to get his condition to improve and are ensuring that Madiba is well-looked after and is comfortable." He also appealed to South Africa and the world to pray for Mandela, his family and the medical team.