An argument followed and the athlete, who is free on bail, soon left the club, said Anneliese Burgess, a spokeswoman for the Pistorius family. Pistorius had been seated in a quiet booth in the VIP section, she said in a statement.
"My client regrets the decision to go to a public space and thereby inviting unwelcome attention," Burgess said.
Pistorius was accosted by "an individual who has now been identified as a Mr. Mortimer," according to the statement.
The altercation happened Saturday night in Sandton, an upscale area in Johannesburg, according to South African media.
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A woman who answered the telephone at The VIP Room, the club where the incident occurred, said club owner Chris Coutroulis was "overseas" and was awaiting reports from club staff who witnessed the interaction.
The club website says it caters to the "nouveau riche" and invites guests to "slip on your diamante dancing shoes or designer suit and dance the night away at the most ostentatious venue in Joburg."
Pistorius, whose running career peaked when he competed against able-bodied athletes in the London Olympics in 2012, faces 25 years to life in prison if found guilty of premeditated murder. He could also be sentenced to a shorter prison term if convicted of murder without premeditation or negligent killing.
Additionally, he faces separate gun-related charges. Closing arguments will be held Aug 7-8.