South African anti-apartheid activist Helen Suzman has died at the age of 91.

The South African Press Association reports that Suzman died peacefully at her home in Johannesburg Thursday.

Suzman, who was white, was one of the few lawmakers who protested against South Africa's former system of discrimination against blacks.

She visited Nelson Mandela during his long imprisonment on Robben Island, and became known as parliament's most effective critic of apartheid.  Twice, she was nominated for the Nobel Peace Prize.

Suzman spent 36 years in parliament - 13 of them as the lone representative of the liberal Progressive Party.  She retired in 1989, as the international movement against apartheid was gaining strength. 

Her daughter, Frances Joel, says a private funeral will take place this weekend.

Some information for this report was provided by AFP, AP and Reuters.