Inkatha Freedom Party (IFP) leader, Prince Mangosuthu Buthelezi, on Wednesday praised the personal sacrifices that anti-apartheid struggle icon Mama Winnie Madikizela-Mandela made for the liberation of South Africa, referring to her as a "big tree" that "has fallen".

"Fellow South Africans, a very big tree has fallen and our nation mourns. Mama Winnie will be remembered all over the world as the Mother of the Nation," Buthelezi said.

"Mama Winnie didn't know that her kids would be orphans when both of them were alive due to imprisonment. Her personal sacrifices for our freedom are celebrated all over. It is remarkable to see the women that Winnie's daughters have become in spite of all their challenges. They are so like her in courage and resilience."

Buthelezi said it was his late cousin, who was a bishop, that first used the title 'Mother of the Nation' to describe Madikizela-Mandela.

He was speaking at the official memorial service of Madikizela-Mandela where thousands of mourners gathered at Orlando Stadium in Soweto.

"Winnie was more than just Madiba's wife, she was a passionate ambassador of justice. She was prepared to walk the path of collision with injustice. I admired her tremendously. We express our sympathy to the family. I send my condolences to the President and the family of the ANC," Buthelezi said.

"We will miss her in time to come. But the deeper sorrow is left for her family. May you find strength in the words of admiration coming from all corners of the world for your beloved mother."

In the end, Buthelezi asked all the men in the stadium to stand and salute Mama Winnie with her clan name, "Ah, Nobandla", a touching moment for many opposed to patriarchy as the salutation is usually reserved for men.

Madikizela-Mandela died on Easter Monday in a Johannesburg hospital. She was 81. She will be laid to rest on Saturday in Johannesburg following a funeral service in Soweto.