Ahmed Kathrada, close friend of former South African President Nelson Mandela, speaks during Mandela's funeral ceremony in Qunu, Dec. 15, 2013. REUTERS

The president of South Africa is not welcome to attend the funeral of an iconic anti-apartheid activist, the family of the deceased said Tuesday. Ahmed Kathrada, who was imprisoned for decades along with former South African president Nelson Mandela, died Tuesday, the BBC reported. He was 87 years old.

Kathrada's family has asked current South African president Jacob Zuma to stay away from the funeral on Wednesday, likely because Kathrada previously asked Zuma to resign, according to a series of tweets from a local journalist.

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Zuma has ordered flags throughout the country to fly at half-mast and said a "special official funeral" would be organized. It appeared that Zuma did not immediately respond to the wishes by Kathrada's family.

Kathrada was expected to be buried Wednesday, but Zuma said he would arrange a special funeral for the activist.

Kathrada wrote an open letter to Zuma asking him to step down from his presidency last year, according to local news outlet News 24.

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"I have always maintained a position of not speaking out publicly about any differences I may harbour against my leaders and my organisation, the ANC. I would only have done so when I thought that some important organisational matters compel me to raise my concerns," Kathrada wrote. "Today I have decided to break with that tradition."

The letter continued:

"And bluntly, if not arrogantly; in the face of such persistently widespread criticism, condemnation and demand, is it asking too much to express the hope that you will choose the correct way that is gaining momentum, to consider stepping down?"

Kathrada and Mandela were sentenced to life in prison for conspiring against the country's white government after he was arrested in 1963. He was imprisoned on the infamous Robben Island for 26 years. South Africa's apartheid laws, against which Kathrada and Mandela led revolts, were made up of "policies of racial segregation under a system of legislation."