Leading South African anti-apartheid activist Ahmed Kathrada, who was one of Nelson Mandela's closest colleagues, died early Tuesday aged 87, Kathrada's charity foundation said.

Kathrada was among those tried and jailed alongside Mandela in the Rivonia trial in 1964, which drew worldwide attention and highlighted the brutal legal system under the apartheid regime.

Kathrada spent 26 years and 3 months in prison, 18 of which were on Robben Island.