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Anneliese Burgess said her client was at the VIP section of the club when he was approached by a man who has since been identified as Jared Mortimer.
"The individual, according to my client, started to aggressively interrogate him on matters relating to the trial," said Burgess.
The paralympic athlete is charged with murdering his law-graduate and model girlfriend, Reeva Steenkamp on Valentine's Day last year. He claims he mistook her for an intruder when he shot her dead through a locked toilet door at his Pretoria home.
The State, however, claims he shot her following an argument.
Elaborating on Saturday's incident, Burgess said: "An argument ensued during which my client asked to be left alone. Oscar soon thereafter left the club with his cousin."
Eyewitness News (EWN) reported that Mortimer claimed Pistorius was drunk and had insulted him and his friends before poking him in the chest.
Mortimer said he pushed Pistorius and he fell backwards on his feet and onto a chair.
According to EWN, bouncers intervened and stopped the brawl.
Officials from the club -- the VIP Room -- which is at the Michelangelo Towers in Sandton, have denied the incident.
Spokesman Perry Mermigas admitted that Pistorius was at the club, but denied that anything out of the ordinary happened.
"We are not aware of this," Mermigas told Sapa.
"[Pistorius] was there but there was no altercation and if there had been, we would have known about it," he said.
Meanwhile, Pistorius regretted visiting the club.
"My client regrets the decision to go to a public space and thereby inviting unwelcome attention," said Burgess.
On Sunday, just several hours after the incident, Pistorius was active on social-networking site, Twitter.
He tweeted a Bible verse, a collage of pictures of his humanitarian work, and an extract from Viktor Frankl's book "Man's Search for Meaning".
The text reads in part: "... The salvation of man is through love and in love. I understood how a man who has nothing left in this world still may know bliss, be it only for a brief moment, in the contemplation of his beloved.
"In a position of utter desolation, when man cannot express himself in positive action, when his only achievement may consist in enduring his sufferings in the right way - an honourable way - in such a position man can, through loving contemplation of the image he carries of his beloved, achieve fulfilment."
The verse from the Bible, Psalm 34:18 reads: "The Lord is close to the broken-hearted".
This was the first time Pistorius had been active on Twitter since the one-year-anniversary of Steenkamp's death.
Back then he tweeted: "No words can adequately capture my feelings about the devastating accident that has caused such heartache for everyone who truly loved -- and continues to love Reeva."
"The pain and sadness -- especially for Reeva's parents, family and friends consumes me with sorrow. The loss of Reeva and the complete trauma of that day, I will carry with me for the rest of my life."
Last week, the defence closed its case in Pistorius's trial in the High Court in Pretoria. Final arguments are expected to be heard on August 7.
Murder accused paralympian Oscar Pistorius allegedly insulted President Jacob Zuma's family while at a night club in Sandton, The Star reported on Tuesday.
Johannesburg businessman, Jared Mortimer was quoted in the paper claiming that Pistorius insulted Zuma's family and his own friends resulting in an altercation on Saturday night.
"I took that personally because I am very good friends with a member of the Zuma family," he said.
Mortimer claimed Pistorius was intoxicated and started to poke him in the chest while they were talking. He then pushed Pistorius away from him and the paralympian fell over a chair.
The club's bouncers helped Pistorius up, but were asked to remove him after he "had a confrontation with another man", Mortimer said.
Beeld newspaper carried a picture of Mortimer shaking hands with former president Nelson Mandela on its front page on Tuesday.