Johannesburg, Apr 3 (AFP): Winnie Mandela, the former wife of South African anti-apartheid icon Nelson Mandela, died on Monday aged 81, triggering an outpouring of tributes to one of the country's defining and most divisive figures.

The firebrand activist died in a Johannesburg hospital, her family said, adding that she had "fought valiantly against the Apartheid state" and that she was known "far and wide as the Mother of the Nation".

Winnie Mandela, who was married to Nelson Mandela for 38 years, played a high-profile role in the struggle to end white-minority rule, but her place in history was stained by controversy and accusations of violence.

Leading the tributes, Nobel laureate archbishop Desmond Tutu described her as "a defining symbol" of the battle against oppression.

"She refused to be bowed by the imprisonment of her husband, the perpetual harassment of her family by security forces, detentions, bannings and banishment," Tutu said.

"Her courageous defiance was deeply inspirational to me, and to generations of activists."

The statement from her family said that she passed away at the Netcare Milpark hospital in Johannesburg.

"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," it added.

In the ruling African National Congress (ANC), head of policy Jeff Radebe described her as "an icon of the revolutionary struggle".

Newly-appointed President Cyril Ramaphosa announced Tuesday evening that a "national official funeral" would be held on April 14, preceded by a public memorial service on April 11.

Most of Winnie's marriage to Nelson was spent apart, with Nelson imprisoned for 27 years, leaving her to raise their two daughters alone and to keep alive his political dream under the repressive white-minority regime.

But her reputation came under damaging scrutiny in the twilight years of apartheid rule.

In 1986, she was widely linked to "necklacing", when suspected traitors were burnt alive by a petrol-soaked car tyre being put over their head and set alight.

In 1990 the world watched when Nelson Mandela finally walked out of prison -- hand in hand with Winnie.

The following year, she was convicted of kidnapping and assault over the killing of Stompie Moeketsi, a 14-year-old boy.

In 1992, the Mandelas separated, and then divorced in 1996, after a legal wrangle that revealed she had an affair with a young bodyguard.

During her old age, she re-emerged as a respected elder who was feted as a living reminder of the late Mandela -- and of the long and much-storied struggle against apartheid.

Just last month, she was shown in television footage joking with Ramaphosa, who paid a courtesy call to her home in Soweto, the township where she lived for decades.

Dressed in full ANC colours of yellow, black and green, she asked Ramaphosa, who is known for his morning runs, "Why don't you get tired?"

"We can't get tired when you have given us work to do'" he told her.

After her death was announced, Ramaphosa described her as "a voice of defiance and resistance" who "was an abiding symbol of the desire of our people to be free".

"For many years, she bore the brunt of senseless brutality of the apartheid state with stoicism," he said.

"Despite the hardship she faced, she never doubted that the struggle for freedom and democracy would triumph and succeed."

Winnie Mandela often criticised the ANC, but she had expressed support for the current leadership of the party, which her husband led to power in the euphoric post-apartheid elections of 1994.

On Monday evening, Ramaphosa returned to her Soweto house as mourners gathered outside, singing struggle-era songs in tribute and praise.

"In African culture, we sing when we're hurt," ANC Women's League official Winnie Ngwenya, 64, told AFP.

African Commission chairman Moussa Faki Mahamat also paid tribute to Winnie Mandela, saying "the continent and beyond" were in grief at her passing.

She "will forever be remembered as a global icon, a fearless campaigner who sacrificed much of her life for freedom in South Africa and for women everywhere," he said on Twitter.

The SABC state broadcaster said she had attended church in Soweto on Easter Friday before being admitted to hospital complaining of flu. She had also suffered from diabetes for some years.

Suggestions that Winnie remained extremely close to Nelson Mandela in his final years were fuelled in a recent book by his doctor.

Vejay Ramlakan wrote that Winnie -- not Mandela's widow Graca Machel -- was with Mandela when he died in 2013. The book was withdrawn by its publishers under pressure from Mandela's family.