Struggle stalwart Ahmed Kathrada is in a stable condition after undergoing surgery relating to blood clotting on the brain on Saturday, his foundation said on Sunday.
"Doctors last night indicated that the operation was successful and he is in a stable condition. However, it would be some time before Kathrada fully recovers," the foundation's director Neeshan Balton said.
He said Kathrada was in good spirits, despite being ill prior to the operation.
The 87-year-old had initially been admitted to hospital for dehydration, but doctors later picked up the clot, which has now been removed, Balton said.
The foundation thanked the public and Kathrada's friends and comrades for well-wishes and support.
"We hope that you continue remembering him in your prayers and take time to reflect on the ideals and values that Kathrada and his generation stood for," Balton said.
Kathrada is one of three Rivonia Trialists who are still alive today; the other two being Andrew Mlangeni and Denis Goldberg.
Along with Nelson Mandela, Walter Sisulu, Govan Mbeki, Raymond Mhlaba and Elias Motsoaledi, the group was sentenced to life imprisonment on Robben Island during the Rivonia Trial in 1964.