Oscar Pistorius has vomited in the dock at his murder trial as he heard graphic details of the injuries sustained by the girlfriend he fatally shot.

The testimony of Professor Gert Saayman, the pathologist who performed the autopsy on Reeva Steenkamp's body, was not broadcast or reported live on Twitter by journalists because of its explicit content under an order from Judge Thokozile Masipa. But journalists were allowed to report the evidence without directly quoting the witness.

The double-amputee runner, hunched over on a bench, reacted to the description of Miss Steenkamp's wounds by vomiting and retching repeatedly, prompting Judge Masipa to briefly halt the evidence to ask chief defence lawyer Barry Roux to attend to his client.

The judge also asked whether Pistorius was able to understand the proceedings. Roux said Pistorius' reaction was not going to change. A bucket was placed at his feet.

Prof Saayman stood for much of his time on the stand, referring to photographs that were not shown to the gallery as he described bullet wounds on Miss Steenkamp's body, one to the right side of the head, one to the right arm and one to the right hip area. He also described exit wounds caused by the bullets and other abrasions and discolouration of the skin, consistent with the impact of a bullet fired through a wooden object such as a door.

There was another wound on one of Miss Steenkamp's hands, Prof Saayman said. Miss Steenkamp, a model and personality on a television reality show, was wearing a pair of sports shorts with a Nike logo and a black vest when she was shot, he said.

Pistorius, the first amputee to run in the Olympics, is charged at the high court in Pretoria with premeditated murder for 29-year-old Miss Steenkamp's shooting death before dawn on February 14, 2013.

Pistorius, 27, says the killing was accidental because he thought his girlfriend was a dangerous intruder when he shot her through the door of a toilet cubicle in his home.

Earlier, prosecutor Gerrie Nel, supported by chief defence lawyer Mr Roux, said Prof Saayman's testimony would have an "explicitly graphic nature" and should not be shown around the world. Judge Masipa then announced a ban on live audio and video broadcasting, and extended the order to live reporting on social media.

"Twitter is not allowed. Blogging is not allowed," Judge Masipa said.

Proceedings can be partly televised and the audio can be broadcast in its entirety under a judge's pre-trial order that sought to balance the right to a fair trial with the intense public interest in the Pistorius case and the principle of open justice. Under the order, some witnesses can choose not to be shown on television.

Earlier, Judge Masipa extended that order, saying "private witnesses are more vulnerable than public figures" and that still photographs of witnesses who requested some discretion cannot be published or disseminated for the duration of the trial, even if they were obtained from sources outside the courtroom.

The new ruling followed the publication in a South African media outlet last week of a photo of a witness whose image was lifted from a publicly accessible website.

Before the adjournment, a security guard who said he spoke with Pistorius soon after the shooting of Miss Steenkamp was challenged by the defence about his recollection of the sequences of the events that night.

The sequence is important for the defence because, if it can prove that Pistorius called security first, it could support the contention that he was seeking help as quickly as possible.

The guard, Pieter Baba, had told the court on Friday that he called Pistorius and was told "everything is fine" on the telephone. Mr Baba said Pistorius then called him back moments later, did not speak, was crying and the second call then ended.

Mr Baba said he was responding to neighbours' reports of gunshots coming from Pistorius' home after 3am on Valentine's Day last year. He drove with a fellow guard to Pistorius' villa and made the call from outside the house.

Mr Baba's statement that he called Pistorius first could back the prosecution's case that the killing was premeditated, and that Pistorius was trying, at least initially, to conceal what he had done.

But today Mr Roux said call records showed Pistorius called security first, but could not speak because he was "indeed crying".

"I'm the one who called him first," Mr Baba insisted