The parents of Reeva Steenkamp have disclosed their belief that their model and law graduate daughter was deliberately killed by Paralympian Oscar Pistorius on Valentine's Day 2013. The couple's revelations were aired in an interview with Australia's Channel Seven on 23 August.

The Steenkamp's comments come ahead of an appeal hearing in which prosecutors aim to reverse the court's verdict that the six-times gold medallist was not guilty of murder. Last year, Judge Thokozile Masipa handed Pistorius a five year jail term for culpable homicide (known as manslaughter in the UK) after ruling that state prosecutors had failed to prove that the athlete had shown "intent" to kill.

During the course of a six-month trial, the prosecution argued that Pistorius had killed Ms Steenkamp on purpose when he shot through a locked toilet door four times. Pistorius' defence team said that he believed an intruder was behind the door.

Last week, prosecutors filed an appeal asking for the verdict to be changed to murder and claim that even if Pistorius did not know that Ms Steenkamp was behind the door, he could have reasonably foreseen that somebody could be killed when he pulled the trigger four times. The appeal hearing is scheduled to begin in November.

"What actually came out in court is not the truth," Barry Steenkamp said in the television interview.

"He got angry, she went off to the toilet, locked herself inside, and then him pulling out the gun and shooting."

Ms Steenkamp's mother, June, said: "He killed her. He admits he killed her.

"She is dead after [Pistorius made] sure she was dead. Why didn't he just let her walk away?"

Pistorius, who is also known as the "Blade Runner" because of his J-shaped leg prosthetics, was eligible for release under "correctional supervision" on 21 August as he has served one-sixth of his five-year sentence. His early release was blocked by South African Justice Minister Michael Masutha because the decision had no legal basis. The decision was sent back to the parole review board for review and could take up to four months.

Mr Steenkamp said that even if Pistorius was convicted of murder by the Supreme Court (which carries a custodial sentence of 15 years), their ordeal as parents would not be over. "It is not finished – not finished I feel by a long way – and I can only give you my feelings after the final verdict," he said.

"If the outcome is going to be a longer sentence, are we going to feel better? I don't know.

"All we want is the truth to come out in the real justice side of the whole scenario."