Mourners from all walks of life yesterday trickled into the main entrance of the Union Buildings in Pretoria to put their names in the condolences book for struggle stalwart Albertina Sisulu.

By late yesterday afternoon, about 20 people had filled in their names, words of remembrance and gratitude for the role she played in ending apartheid.

Sisulu died at her home in Linden, Johannesburg, on Thursday night at the age of 92.

Condolences books were also available to the public at her Linden home, at Tuynhuys, in Cape Town, and at the house on Khumalo Street, Soweto, in which she had lived with her husband, Walter.

Harold Maloka, spokesman for the Ministry for Performance Monitoring and Evaluation, said flags outside government buildings would fly at half-mast until the evening before the funeral on Saturday. The condolences books will be accessible until Friday evening.

Government ministers, members of the diplomatic corps and the public are expected to attend the memorial service to be held on Thursday at the Pretoria City Hall at 2pm.

Tributes to Sisulu continued to pour in yesterday, with the Mandela family describing her as "humble" and having a deep love for people, especially the poor.

Nelson Mandela's grandson, Mandla, said on behalf of the family on Sunday that, even though "we were alive to the reality that she was 92 years old, she was in such good health that her passing came as an absolute shock to our family".

He said Sisulu was "indeed regarded by many as the mother of our struggle for freedom in South Africa".

"She has been the pillar of the movement during the most difficult time of our struggle, when her husband and many others were languishing in jail."

"It is well known that the Sisulus and the Mandelas share a strong bond that spanned generations.

"They do not share these ties only because of their common dedication to the struggle for liberation but also because Evelyn Mandela [Nelson Mandela's first wife] and Walter Sisulu are cousins."

Mandla Mandela said it was because of those ties that Sisulu was the primary guardian and caregiver of Evelyn's children during the long period of Mandela's incarceration.

"As a family, we will forever be indebted to the role that Mama Sisulu played in our family," said Mandela.