Former South African President Nelson Mandela is now in critical condition, officials said Sunday, according to CNN.

Mandela's condition worsened in the past 24 hours, the South African president's office said, citing Mandela's medical team.

He has been hospitalized in Pretoria since June 8 for a recurring lung infection. Previously, authorities had described his condition as serious but stable.

"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 is in good hands," President Jacob Zuma said in a written statement, referring to Mandela's tribal name.

Mandela, 94, has become increasingly frail over the years and has not appeared in public since South Africa hosted the World Cup in 2010.

His history of lung problems dates to when he was a political prisoner on Robben Island during the apartheid era, and he has battled recurrent respiratory infections.

Considered the founding father of South Africa's democracy, Mandela became an international figure while enduring 27 years in prison for fighting against apartheid, the country's system of racial segregation.

South Africa's governing African National Congress noted "with concern" Sunday the change in Mandela's health.

"The African National Congress joins the presidency in calling upon all of us to keep President Mandela, his family and his medical team in our thoughts and prayers during this trying time," it said, according to CNN.

In 1993, Mandela and then-South African President F.W. de Klerk jointly won the Nobel Peace Prize.

The iconic leader was elected the nation's first black president a year later, serving only one term, as he had promised.

Even as he has faded from the spotlight, he remains popular and is considered a hero of democracy in the nation. Last year, South Africa launched a new batch of banknotes with a picture of a smiling Mandela on the front.

Mandela's impact extends far beyond South African borders. After he left office, he mediated conflicts in Africa and the Middle East.

He has in the past criticized the U.S. through Israel, hinting in 2003 that then- President George W. Bush had no foresight because “Their friend Israel has got weapons of mass destruction, but because it’s their ally they won’t ask the U.N. to get rid of it. They just want the oil.”

Mandela also said once that “if the Palestinians are not free, no one is free”, a statement which anti-Israel groups have taken advantage of to accuse Israel of applying a policy of “apartheid” towards Arabs.