The prosecutor in the murder trial of Oscar Pistorius ended his five-day cross-examination of the double amputee track athlete on Tuesday with a stark summary of how he shot his girlfriend, insisting he killed her deliberately after an argument.

"You fired four shots through the door whilst knowing that she was standing behind the door," said prosecutor Gerrie Nel, known in South Africa as "The Pitbull" for his hectoring style of questioning.

"She was locked into the bathroom and you armed yourself with the sole purpose of shooting and killing her."

"That is not true," said 27-year-old Pistorius, who faces life in prison if convicted of murder.

Pistorius has broken down in tears on many occasions during the questioning, and at one point retched into a bucket on the witness stand after being shown grisly pictures of Reeva Steenkamp after the shooting on Valentine's Day last year.

He insists he killed the 29-year-old law graduate and model accidentally after mistaking her for an intruder hiding behind a closed toilet door.

On Tuesday he told the court he had pulled the trigger without thinking after hearing a noise behind the door, out of terror and fear that his and Steenkamp's lives were in danger."

Reuters