The family spokesperson says the former wife of Nelson Mandela, once described as the "Mother of the Nation" by many South Africans, died "surrounded by her loved ones."
Winnie Madikizela-Mandela, who emerged as a combative anti-apartheid campaigner during her husband Nelson Mandela's decades in jail but whose reputation was later tarnished by allegations of violence, died on Monday at the age of 81.
The woman many South Africans once described as the "Mother of the Nation" and a champion of the black majority, died "surrounded by her family and loved ones," according to a statement released by Madikizela-Mandela's family.
Madikizela-Mandela had been in and out of hospital since the start of the year, according to her family. She had back surgery a year ago.
"She fought valiantly against the apartheid state and sacrificed her life for the freedom of the country," family spokesman Victor Dlamini said.
"She kept the memory of her imprisoned husband Nelson Mandela alive during his years on Robben Island and helped give the struggle for justice in South Africa one its most recognisable faces."
The nature of her illness was not disclosed.
A crowd of around 200 people soon gathered outside her Soweto home, singing and dancing. A number of national and local politicians arrived and police closed the street to traffic.
TRT World's Gladys Njoroge Morgan reports.
'We lost a mother'
President Cyril Ramaphosa led an outpouring of grief over her death in South Africa.
"Today we have lost a mother, a grandmother, a friend, a comrade, a leader and an icon," said Ramaphosa, who was expected to visit the family home later on Monday.
Retired South African cleric and anti-apartheid campaigner Archbishop Desmond Tutu said, "Her courageous defiance was deeply inspirational to me and to generations of activists."
Energy Minister Jeff Radebe expressed condolences on behalf of the ruling African National Congress (ANC) and urged those who loved her to celebrate her.
A FREEDOM FIGHTER. A STALWART AND ICON OF OUR STRUGGLE. A DEDICATED REVOLUTIONARY. A MOTHER OF THE NATION. WINNIE NOMZAMO MADIKIZELA-MANDELA 26 September 1936 - 2 April 2018 #MHSRIP #RIPWinnieMandela pic.twitter.com/gHZGfbxMF5— African National Congress (@MYANC) April 2, 2018
Born on September 26, 1936, in Bizana, Eastern Cape province, Madikizela-Mandela became politicised at an early age in her job as a hospital social worker.
The 22-year-old Winnie caught the eye of Mandela at a Soweto bus-stop in 1957, starting a whirlwind romance that led to their marriage a year later.
After Nelson Mandela was jailed for life in 1964 for sabotage and plotting to overthrow the government, Madikizela-Mandela campaigned tirelessly for his release and emerged as a prominent anti-apartheid figure in her own right, undergoing detention, banishment and arrest.
She punched the air in the clenched-fist salute of black power as she walked hand-in-hand with Mandela out of Cape Town's Victor Vester prison on February 11, 1990.
For husband and wife, it was a crowning moment that led four years later to the end of centuries of white domination when Mandela became South Africa's first black president.
But their marriage began to fall apart in the years after his release. The couple divorced in 1996, nearly four decades after they were married. They had two children together.
The end of apartheid marked the start of a string of legal and political troubles for Madikizela-Mandela.
As evidence emerged in the dying years of apartheid of the brutality of her Soweto enforcers, the "Mandela United Football Club", her soubriquet switched from 'Mother' of the nation to 'Mugger'.
Blamed for the killing of activist Stompie Seipei, who was found near her Soweto home with his throat cut, she was convicted in 1991 of kidnapping and assaulting the 14-year-old because he was suspected of being an informer.
Her six-year jail term was reduced on appeal to a fine.