Madikizela-Mandela was jailed several times for her part in the fight against white-minority rule and she campaigned for the release of her husband at home and abroad.

But her marriage to Mandela began to fall apart in the years after he was released from prison in 1990. The couple divorced in 1996, nearly four decades after they were married. They had two children together.

In an obituary, Reuters' Africa buearu chief Ed Cropley said Madikizela-Mandela was hailed as the mother of the 'new' South Africa but her legacy as an anti-apartheid heroine was undone when she was revealed to be "a ruthless ideologue prepared to sacrifice laws and lives in pursuit of revolution and redress".

"Her uncompromising methods and refusal to forgive contrasted sharply with the reconciliation espoused by her husband Nelson Mandela as he worked to forge a stable, pluralistic democracy from the racial division and oppression of apartheid,"  he wrote.

"The contradiction helped kill their marriage and destroyed the esteem in which she was held by many South Africans, although the firebrand activist retained the support of radical black nationalists to the end."