Former president Jacob Zuma has spoken for the first time about the pain of losing his son, Vusi Nhlakanipho Zuma, to whom he paid tribute as being different from all his children.

A grief-stricken Zuma, who said he had also been battling a bout of flu, spoke at his 25- year-old son's funeral at Rhema Bible Church in Randburg, Joburg, on Saturday.

In a 10-minute tribute, he shared with mourners intimate details of his memories with Vusi and how they shared a special bond, more so because he was "very young when his mother passed away".

Vusi was the last-born of Zuma's five children with the late Kate Zuma, who died after taking an overdose of sleeping pills and malaria drugs in 2000.

Almost choking on his own words at times, Zuma also revealed his son's death had put a strain on him.

"It is quite an experience that many parents go through, to lose a child. I have quite a sizeable number of children but it is the first time I am losing a child so it has put a weight on my being (and) difficult to live with it," he said.

"Vusi was one of my boys that I loved so much. There was one thing that perhaps separated him from the others - when his mother passed away he was very young."

Zuma said he had lived with Vusi for some time at a government house, where they bonded by watching cartoons and swimming together. He said they became best of friends.

"One of the things he made me appreciate was his tendency to watch Popeyes (cartoons)," Zuma said.

"At first I was keen to watch my channels and I realised if I want to do so I must go to another room because the man just looked at the Popeyes. I even began to know their names and we became great friends. "

He said Vusi was "always a sweet gentleman who practised nonracialism and that could be seen in the kind of friends he had".

A visibly pained Zuma then turned to the media, claiming its negative reporting on him had hurt his son and worsened his health.

Vusi Nhlakanipho Zuma was diagnosed with Systemic Lupus Erythematosus, commonly known as lupus, at the age of 17 in 2009 when his father first became president. He died on July 1 aged 25.

"Those who know the disease say you don't need to be emotional at any given time because once you are emotional you trigger it," Zuma said.

"I am saying this because some of my children came to me and said: 'Dad, we do not want media at the funeral'.

"They said the media has been very harsh on this family. Vusi suffered many times. He had to swallow things said about his father and that activated the lupus to be more active. And therefore in our view [that] harsh treatment by the media makes us feel they must have played some role."

Zuma said he had told the media in the past that when they wrote about an individual they should remember those individuals had relatives who may not like what they wrote.

"Find a way to say it."

Zuma was flanked by his grandchildren and wives, including his estranged wife, Nompumelelo Ntuli-Zuma.

Vusi's siblings described him as a loving person whose death had left a void in their lives.

He was buried at the West Park Cemetery next to his mother.