Oscar Pistorius has been accused of trying to intimidate a friend of Reeva Steenkamp in his murder trial by asking her "how can you sleep at night?"
The Paralympian apparently whispered the comment to Kim Myers, a close friend of Steenkamp, whom Pistorius is accused of murdering, as he passed her in court.
Pistorius denies murder and claims he believed Steenkamp was an intruder when he fatally shot her in the early hours of Valentine's Day, 2013.
Myers said Pistorius said the comment under his breath but she confirmed it was what she heard, South African paper City Press reported.
Pistorius allegedly asked Reeva Steenkamp's friend 'how do you sleep at night?'
The paper reported Myers was visibly upset after Pistorius passed her and police officers approached her to establish what happened.
The Guardian reported Myers' lawyer Ian Levitt said: "My client Kim Myers was approached by Oscar #Pistorius in court today and, in a very sinister tone, was asked: 'How can you sleep at night?'
"My client views this unwelcome approach as extremely disturbing and I have been in contact with the NPA."
The NPA is the National Prosecuting Authority, which has the power to initiate criminal proceedings in South Africa.
The Guardian also reported Brian Webber, from Pistorius' legal team, said: "I'm not even going to dignify that with a comment. It's grossly untrue. He never said anything of the sort."
Kim Myers claimed Pistorius asked her 'how do you sleep at night?'
Earlier on Tuesday, the trial heard Pistorius had introduced Steenkamp as "my fiancee" to a neighbour days before he shot her to death.
Michael Nhlengethwa, who lived with Pistorius in their gated Pretoria community, told the trial he met Steenkamp on the Sunday before she died and told Pistorius: "This one is for keeps."
Pistorius denies murder and claims he believed Steenkamp was an intruder when he fatally shot her in the early hours of Valentine's Day, 2013.
Nhlengethwa claimed not to socialise regularly with the Paralympian but said: "Oscar is the type of person who if he sees me, he will stop, get out of his car and greet me."
He added Steenkamp had hugged him the one time they met.
Nhlengethwa, who was called as a witness for the defence, said he was woken by "very high" screaming on the night of the shooting, five days after he met Pistorius and Steenkamp.
"Then we started hearing a man crying very loud." he said. "Something was wrong. We started panicking.
"There is a difference between normal crying and crying when you are in danger, when you need help. We felt probably he was in danger. It was very loud."
Earlier in the trial, neighbours have claimed they heard a high-pitched scream on the night of the shooting, which they believed was from a woman but Pistorius said was him.
Prosecutor Gerrie Nel asked Nhlengethwa whether he heard gun shots on the night. The witness said: "I did not really hear anything in terms of the gun shots."