SOUTH African prosecutors have said they will file appeal papers in the next few days against the verdict and sentencing in the case of Oscar Pistorius, who was given a five-year prison term after being convicted of culpable homicide for killing his girlfriend.

The National Prosecuting Authority's decision to appeal could see the Olympic runner face a murder charge again for shooting Reeva Steenkamp, and a minimum of 15 years in prison if he is found guilty on appeal.

Pistorius, the 27-year-old double-amputee athlete, was acquitted of murder by Judge Thokozile Masipa last month for shooting Ms Steenkamp multiple times through a toilet door in his home in Pretoria. He said he mistook her for a night-time intruder. Judge Masipa found him guilty instead on a charge comparable to manslaughter.

The NPA said in a statement its decision to appeal was based on a "question of law", meaning it believes that Judge Masipa misapplied the law when she acquitted Pistorius of murder.

"The merits and the demerits of the NPA's argument ... will become evident when we file papers for leave to appeal," the NPA, South Africa's national prosecuting body, said. "The prosecutors are now preparing the necessary papers in order to be able to file within the next few days."

Prosecutors have to apply initially to Judge Masipa for permission to appeal within 14 days of Pistorius's October 21 sentencing.

Pistorius's lawyer, Brian Webber, declined to comment.

Pistorius started serving his prison sentence last week. He is eligible for release after 10 months and would then complete the remainder of his sentence under house arrest.