Claims that Oscar Pistorius slurred South Africa's president Jacob Zuma by saying he would urinate on the national leader have been hotly denied by the runner's family.

Pistorius' camp spoke out in defence of the murder accused athlete following a confrontation in a nightclub during which he reportedly told reveller Jared Mortimer: "Zuma works for us. I'll piss on Zuma."

Mortimer, accused of aggressively confronting Pistorius about the death of Reeva Steenkamp, claimed he had been left shocked by the troubled star's outburst.

The fracas happened when Mortimer and Pistorius got into a row at the VIP Club in an upmarket area of Johannesburg.

Recounting the incident to The Juice website, Mortimer said: "Pistorius was going on about how influential his family is and how connected they are.

''He even pulled out his phone to show me pictures of armoured cars. He said: 'My family owns SANDF. Zuma works for us. I'll piss on Zuma."

Mortimer claimed he was so offended that he had to put his drink down. "I took that personally because I am very good friends with a member of the Zuma family," he said.

The allegations have been strongly denied by Pistorius' uncle Leo, who said there was "absolutely no truth" in it.

In a statement, he said: "We wish to categorically state that there is absolutely no truth to this man's assertions that Oscar, for instance, insulted the president of South Afric.

"Oscar was at school with one of President Zuma's sons and liked him a lot. Oscar also has great appreciation of President's Zuma's extraordinary support of the paralympians."

He added about the nightclub episode: "My investigations indicate that Mortimer was the aggressor and eyewitnesses confirm this."