- The sentence is "disproportionate to the crime," prosecutors say
- Famed athlete has been described as a "fallen hero" who will never be at peace
- No comment from Pistorious family on the appeal
"The sentence of six years imprisonment, in all the circumstances, is disproportionate to the crime of murder committed," the National Prosecuting Authority (NPA) said in a written statement. The NPA said that it hoped the appeal will clarify sentencing principles in South Africa, where serious crimes have prescribed minimum sentences.
This is the latest development in a dramatic case that has captivated South Africans and the world.
A dragged-out legal drama
Pistorious was originally convicted of manslaughter in 2014 after months of hearings, but a higher court reversed that to murder last year, leading to the latest sentencing.
Judge Thokozile Masipa surprised many when she sentenced the former Olympian to six years earlier this month. The minimum sentence for murder in South Africa is 15 years, but individual judges are given leeway if there are "substantial and compelling" reasons to do so.
Masipa cited mitigating circumstances for the lesser punishment, saying Pistorius is genuinely remorseful and a good candidate for rehabilitation.
She described him as a "fallen hero" who will never be at peace.
"It must be one of the most difficult things for any accused to have to face the victims of his crime and to apologize," the judge told the court.
A spokesperson for the Pistorius family said they would not comment at this time.
Despite a series of hearings, questions remain about exactly what happened at 4 a.m. in the early hours of Valentine's Day three years ago. Stunned fans have wondered how the celebrated former Olympian and Paralympic gold medalist turned into a killer.
Pistorius killed Reeva Steenkamp at his home in an upscale Pretoria neighborhood -- an act he says was an accident, after he mistook her for an intruder, but one the prosecution called a deliberate act after the two had an argument.
The prosecution has said that Pistorius had a violent streak, and that he murdered his lover after a late-night argument. But the judge said there was no evidence supporting the accusation that the two had a fight.
The defense has always maintained that the amputee track star mistakenly believed Steenkamp was an intruder and feared for his life when he shot through the door.