CNN reported that Zindzi Mandela, the youngest daughter of anti-apartheid activists Nelson Mandela and Winnie Mandela, has died. She was 59 years old. 

The South African Department of International Relations and Cooperation confirmed her passing but has yet to release her cause of death. The department is still awaiting the information and expects to release a statement at a later time.

Zindzi passed early Monday morning at a Johannesburg hospital, according to a statement from the office of South African President Cyril Ramaphosa.

"I offer my deep condolences to the Mandela family as we mourn the passing of a fearless political activist who was a leader in her own right," Ramaphosa said in the statement. "Our sadness is compounded by this loss being visited upon us just days before the world marks the birthday of the great Nelson Mandela."

The Nelson Mandela Foundation said in a statement that Zindzi will be remembered for her “rich and extraordinary life, marked by many iconic moments.”

“We will also remember her as a special soul. She worked with the Foundation on many projects over the years, for instance the book Hunger for Freedom, by author Anna Trapido. We valued her generosity, her warmth and her sense of humour,” the statement read. “She was always patient in responding to our requests for information and other forms of assistance. And we admired her strength in dealing with life’s challenges and tragedies.”

The foundation also tweeted Monday to honor Nelson’s eldest son, Madiba Thembekile, who died on the same day in 1969.

Zindzi, who was South Africa’s ambassador to Denmark, rose to public prominence in 1985 when then President P.W. Botha offered to release her father from prison if he denounced violence committed by the Africa National Congress. Zindzi read aloud Nelson's rejection letter on the proposal at a public meeting, reports the New York Post.

Zindzi sparked controversy last year when she called for white-owned land to be returned to Black South Africans.

“Dear Apartheid Apologists, your time is over. You will not rule again. We do not fear you. Finally #TheLandIsOurs,” she wrote.

Minister of International Relations Naledi Pandor said Zindzi served the country well.

"Zindzi will not only be remembered as a daughter of our struggle heroes, Tata Nelson and Mama Winnie Mandela, but as a struggle heroine in her own right. She served South Africa well," Pandor said.

In a statement, the Mandela family said that a memorial service and funeral arrangements will be announced in the upcoming days.

Zindzi is survived by her husband and four children, reports the Associated Press.