JOHANNESBURG (AP) - The office of the South African president says Nelson Mandela's health improved overnight, and his condition remains critical but is now stable.

President Jacob Zuma's office said in a statement Thursday that he received the update from the medical team that is treating the 94-year-old anti-apartheid leader at a Pretoria hospital.

Zuma, who visited Mandela on Thursday, said in the statement that the former president is "much better" than when Zuma visited him on the previous night.

His office says it is disturbed by what it calls rumours about Mandela's health. Unconfirmed reports and speculation about Mandela have been swirling on social media and other forums.