JOHANNESBURG (AP) — Millions of South Africans prepared to say goodbye to anti-apartheid icon Winnie Madikizela-Mandela as her emotionally charged official funeral began Saturday in Soweto, where she lived until her death on April 2 at 81.

Thousands of mourners packed a 40,000-seat stadium to bid farewell to the powerful figure who will be buried as a national hero, after lively debate over how she should be remembered.

Often called the "Mother of the Nation" and "Mama Winnie," Madikizela-Mandela fought to keep South Africa's anti-apartheid struggle in the international spotlight while her husband, Nelson Mandela, was imprisoned.

Condolences have poured in from around the world in remembrance of one of the 20th century's most prominent political activists.

Civil rights leader Jesse Jackson, who attended the funeral, said on Friday that Madikizela-Mandela was responsible for making the anti-apartheid movement "a global struggle."

"She never stopped fighting. She never stopped serving," he told reporters. "She never left the belly of the beast."

Many memorializing Madikizela-Mandela have recognized her as a political force in her own right.

U.N. Secretary-General Antonio Guterres called her an "international symbol of resistance" whose extraordinary life had an impact on millions of people around the world.

"In apartheid South Africa, the combination of patriarchy and racism together meant that black women confronted enormous obstacles from the cradle to the grave - making her own achievements all the more exceptional," he said Friday at a memorial in New York, not mentioning Nelson Mandela at all.

The young Madikizela-Mandela grew up in what is now Eastern Cape province and came to Johannesburg as the city's first black female social worker. Not long after, she met African National Congress activist Mandela and the couple married in 1958, forming one of the most storied unions of the century.

After Mandela was imprisoned, Madikizela-Mandela embraced her own leadership in the freedom struggle with steely determination and at great personal sacrifice.

For years, she was routinely harassed by apartheid-state security forces, imprisoned and tortured. In 1977, she was banished to a remote town to separate her from the heart of the movement she led in Soweto.

It took a toll. When Madikizela-Mandela returned from exile she became involved with a group of young men known as the Mandela United Football Club, who were widely blamed for violence in Soweto.

They were accused of the disappearances and killings of at least 18 boys and young men and the group's leader was convicted of killing a 14-year-old boy, nicknamed "Stompie," who was accused of being a police informer.

In 1991, a court found Madikizela-Mandela guilty of the boy's kidnapping and assault and sentenced her to six years in jail. She appealed and was found guilty of being an accessory, and the sentence was reduced to a fine and a suspended prison term. Madikizela-Mandela denied any knowledge of any killings.

Mandela divorced her in 1996, claiming infidelity and saying that after his release from prison, his wife made him "the loneliest man."

Though she fought fiercely for democracy, Madikizela-Mandela floundered in a political career after the first free elections in 1994. Mandela fired her as one of his deputy ministers and her stints as a lawmaker, a post she held until her death, were lackluster.

At her official memorial service on Wednesday, family members and supporters defended her legacy against detractors.

"She gave everything she had," said ANC deputy secretary general Jessie Duarte. "For those of you whose hearts are unforgiving, sit down and shut up. This is our hero. This is our heroine."