The youngest daughter of former South African leader Nelson Mandela has died suddenly at age 59.

Zindzi Mandela, who was serving as the ambassador to Denmark at the time of her death, is survived by her four children and husband Molapo Motlhajwa.

Local media reports indicate she passed away on Sunday night at a hospital in Johannesburg, although the cause of death remains unknown.

Ms Mandela's anti-apartheid activists father died in December 2013, while her mother Winnie Madikizela-Mandela passed away in April 2018.

The death has been confirmed by members of the high-profile family, with Ms Mandela's son Bambatha posting a photo of his late mother on Instagram with the caption "Lala ngo xolo Madlomo", which translates to English as "Sleep in peace Madam".

The post attracted an outpouring of grief and sympathy from fellow social media users.

Zindzi Mandela was born on December 23, 1960 in Soweto, and her famous father was sent to prison when she was just 18 months old - where he remained until 1990.

Zindzi Mandela studied law at the University of Cape Town before following in her family's political footsteps, temporarily serving as the nation's First Lady following her father's election and her parents' divorce.

She held the post until Nelson Mandela married Graça Machel in 1998.

Last June, Ms Madela sparked controversy after her official Twitter account posted a series of divisive posts, referring to "trembling white cowards who are the thieving rapist descendants of Van Riebeck (sic)" and "uninvited visitors who don't want to leave".

Jan van Riebeeck was the Dutch colonial administrator who founded Cape Town in the 1600s and essentially paved the way for white settlement in Southern Africa.

More to come.

Originally published as Nelson Mandela's daughter dead at 59