HALI YA MANDELA TETE

(CNN) -- Former South African President Nelson Mandela is now in critical condition, officials said.

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.

Revolutionary and politician Nelson Mandela

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

The anti-apartheid hero has been in and out of the hospital in recent years.

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

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.