Jared Mortimer, who he had the altercation with, claims the Paralympic athlete was drunk.

A spokeswoman for Pistorius said the row happened after Mortimer began to "aggressively interrogate" him about the murder trial, which began in March.

The 27-year-old six-time Paralympic gold medallist denies deliberately killing his girlfriend Reeva Steenkamp on February 14 last year.

He says he fired shots through a locked toilet door in his Pretoria home thinking there was an intruder.

Three of the four shots hit and killed Steenkamp, 29, who was in the toilet.

The weekend's argument happened at a club in the upmarket Sandton business district.

Pistorius' spokeswoman added: "Our client regrets the decision to go into a public place and thereby invite unwelcome attention."

Mortimer claims the argument began when Pistorius insulted his friends and South African President Jacob Zuma.

Members of Oscar Pistorius' family have spoken of the athlete's "escalating sense of loneliness and alienation", in a statement written after the weekend's altercation  ©AFP/Getty Images



He said the athlete started to poke him in the chest as they spoke.

The businessman said he then pushed Pistorius away from him and he fell over a chair.

Pistorius was in the VIP section of the nightclub at the time.

His family has leapt to his defence.

In a statement from his uncle Leo Pistorius, the family said claims he criticised Zuma were untrue.

"Those of us closest to him have been witness to his escalating sense of loneliness and alienation," it added.

"This, we believe, is underlying some of his self-harming behaviour.

"Oscar is grappling with an extreme level of emotional pain that is manifesting itself in some of his recent unwise actions and choices."