PRETORIA, South Africa -- Nelson Mandela's ex-wife, Winnie Madikizela-Mandela, has died at the age of 81, according to her family and personal assistant.

Madikizela-Mandela, known to many in South Africa as “The Mother of the Nation,” had been ill for a number of years and was most recently admitted to the hospital for a kidney infection.

Her personal assistant‚ Zodwa Zwane‚ first confirmed Madikizela-Mandela's death on Monday afternoon.

“It is with profound sadness that we inform the public that Mrs Winnie Madikizela-Mandela passed away at the Netcare Milpark Hospital‚ Johannesburg‚ South Africa on Monday April 2‚ 2018," Madikizela-Mandela's family said in a statement. "She died after a long illness‚ for which she had been in and out of hospital since the start of the year. She succumbed peacefully in the early hours of Monday afternoon surrounded by her family and loved ones."

Family spokesperson Victor Dlamini said details of a memorial and funeral service would be released soon.

Madikizela-Mandela was born in 1936 and moved to Johannesburg to study social work after graduation. She met lawyer and anti-apartheid activist Nelson Mandela in 1957 and the two married a year later. They had two children together.

During her ex-husband’s 27-year imprisonment for his fight against apartheid, Madikizela-Mandela campaigned for his release and the rights of black South Africans despite being arrested and banished by the apartheid government and constant harassment by security police.

The former first lady’s life was not without controversy. In 1991‚ she was convicted of kidnapping and being an accessory to the assault of Stompie Seipei‚ a young activist who was killed by one of her bodyguards.

Madikizela-Mandela’s bodyguards had abducted Seipei‚ 14‚ in 1989‚ along with three other youths‚ from the home of Methodist minister Paul Verryn.

Her six-year jail sentence was reduced to a fine and a two-year suspended sentence on appeal.

Her marriage to Mandela began to flounder a few years after his release and the couple divorced in 1996‚ 37 years after their marriage.

After the first democratic election in 1994‚ Madikizela-Mandela became an MP and was appointed deputy minister of arts and culture. She was fired by Mandela after an unauthorized trip to Ghana.

She had been a member of Parliament ever since‚ despite limited appearances in Parliament in the past few years.

In 2016‚ she was conferred an Order of Luthuli in Silver during the National Orders Awards ceremony for her excellent contribution to the fight for the liberation of the people of South Africa.