Oscar Pistorius has insisted to the High Court in Pretoria that he never treated girlfriend Reeva Steenkamp "badly" during their relationship.

The 27-year-old is accused of murdering the South African model, whom he shot dead through a bathroom door at his home on Valentine's Day last year.

The double amputee took to the witness stand for the fourth time to be cross-examined by prosecutor Gerrie Nel, who sifted through messages exchanged between the couple through phone service Whatsapp.

Nel claimed that a number of messages, including one which revealed that Pistorius had asked Steenkamp to stop chewing gum, showed that the athlete had disregarded her feelings.

Pistorius responded in court by saying: "I didn't treat her badly."

Asked by Nel if his girlfriend had been untruthful about how much Pistorius picked on her, the sportsman replied: "She never lied."

The prosecution also read out a message in court from Steenkamp, responding to accusations from Pistorius that she flirted with another man at a party.

Pistorius denies murder by maintaining that he mistook his girlfriend for an intruder when he fired the shots.