Jacob Zuma has for the first time claimed that his son Vusi died from poisoning - and that the plan was to "hurt" the former president.

Zuma made the startling revelation in a Zoom conversation with his other son, Duduzane, that was posted on YouTube on Tuesday. By 5pm on Wednesday the video had been viewed 20,500 times.

In his virtual conversation with Duduzane, Zuma tells him that Vusi died in 2018 of poisoning - even though at the time of his death, the Zuma family said the 25-year-old had died from lupus.

At the time of Vusi's death, a statement from the Zuma family said: "Nhlakanipho Vusi Zuma departed on July 1 2018 from complications of systematic lupus erythematosus‚ simply known as lupus."

But in the Zoom conversation with Duduzane, Zuma claims that his son was in fact poisoned - and that the people who poisoned Vusi did so to inflict pain on him.

"Here was a young man growing very bright, really with a big future, but he had to die," said Zuma.

"He had an ailment that you can control until you are very old, but he passed away very suddenly. Now that I know what took him is what pains me even more. I now know that it was people who were trying to kill me … who then took a decision to create something that would pain me, and I now know.

"It was a failure to take your life that they went to the young man in a manner that is very cruel because they interfered with his treatment in order to poison him. Now I know, so the pain has not just doubled but has tripled in me - because here I lose, for the first time, my child who had many years to live and it was in the place of me [that he was poisoned]."

In the conversation, Zuma also claims that he was poisoned and is still amazed that he is alive. For this survival he thanks "my ancestors and my God", while Duduzane keeps adding how the poison had weakened his father at the time.

Duduzane recalled his father telling him that he could not finish a presentation at an ANC national executive committee meeting because of the effects of the poisoning.

Furthermore, Duduzane - who is doing most of the talking in the conversation - alleges that Zuma was once advised by his presidential staff and doctors to postpone his presidential inauguration, but he refused and went ahead with it despite his illness.

It was after this that Duduzane claimed to have flown to Russia with his father to get medical treatment.

Zuma expressed gratitude to "my friend" from Russia - understood to be the country's leader Vladimir Putin.

"I knew that once I went there [Russia], this would be defeated - and it was defeated, and they finally found out that it was poison," said Zuma.