The legendary South African civil rights activist and politician Winnie Madikizela-Mandela died on Monday at the age of 81, her personal assistant and family said.

A leading figure in the ruling African National Congress party, Mandela — who was born in Bizana (Eastern Cape province) in 1936 — had suffered from a kidney infection that led to her hospitalization in January.

Her assistant, Zodwa Zwana, first confirmed her death to the local daily The Times, while her family later released a statement in which it called Mandela "one of the greatest icons of the struggle against apartheid."

The statement added that she had died peacefully after a long illness, having been "in and out of hospital since the start of the year."

Winnie Mandela gained prominence in South African politics as the spouse of the country's first black president, Nelson Mandela, who ascended the presidency in 1994 after having spent 27 years as a political prisoner for his anti-apartheid activism.

The Mandelas met in 1957 and wed in 1958. She became his second wife, following Mandela's divorce from Evelin Ntoko Mase in 1957.

They eventually separated in 1992, two years after Mandela's release from prison, and completed their divorce in 1996.

In 1994, the year that saw South Africa's first democratic and multiracial post-apartheid elections, Winnie Mandela was elected to the National Assembly and served as deputy minister of arts, culture, science, and technology for 11 months before being dismissed after allegations of corruption emerged.

Between 1993-97, she was chosen to head the ANC's Women's League.

In 2003, she was sentenced to five years in prison on a conviction of 43 counts of fraud and 25 of theft, although an appeals judge later overturned the theft conviction while upholding the one for fraud, thus reducing her sentence to only three years and six months of suspended imprisonment.

Nevertheless, she remained an important figure in South African politics — many knew her as "Mother of the Nation"  — and was continuously re-elected as assemblywoman up to the 2014 general election.

"The Mandela family are deeply grateful for the gift of her life and even as our hearts break at her passing‚ we urge all those who loved her to celebrate this most remarkable woman," read her family's statement.