June Steenkamp, the mother of Reeva who was shot dead by paralympian Oscar Pistorius, has told the UK-based Daily Mirror she was "unmoved" by his apology.

"I look at Oscar the whole time to see how he is coping, how he is behaving. I'm obsessed with looking at him, it's just instinctive, I can't explain it," said Steenkamp.

"I keep thinking, 'let me see how he's taking this'. He has been very dramatic, the vomiting and crying... I don't know whether he's acting."

The UK Press Association reported on Thursday on the Daily Mirror's interview with Steenkamp, who said it was "very traumatic" to listen to the graphic detail of the case.

She said she was prepared for his emotional apology when he took the stand on Monday.

"It left me unmoved. I knew it was coming. My lawyers had prepared me for it.

"I cried for the first time, ‘Yes', but not because he apologised, because of the suffering and agony that my darling daughter went through and because I will never have her again."

Pistorius is facing a charge of premedited murder after firing four shots through a locked bathroom door, of which three hit and killed Steenkamp, on Valentine's Day last year.

He has said it was an accident and that he had feared for his and Reeva's lives after believing an intruder had entered his home in a security estate in Pretoria.