The Paralympian could have been jailed for life for killing his girlfriend but the judge decided six years would be sufficient.
Prosecutors in South Africa are to make a fresh attempt to get Oscar Pistorius’ six-year murder sentence increased.
The National Prosecuting Authority (NPA) says it will file papers on Friday.
Two weeks ago, it asked the country’s High Court to overturn Pistorius’ sentence but the request was thrown out.
Now it is taking its case to the Supreme Court of Appeal in Bloemfontein.
The 29-year-old runner shot and killed his girlfriend Reeva Steenkamp at his home on Valentine’s Day in 2013.
He initially served one year of a five-year prison sentence for manslaughter, but the conviction was later overturned by an appeals court.
Pistorius was then convicted of the more serious charge of murder.
He could have been jailed for life but Judge Thokozile Masipa decided six years would be sufficient.
The sentence provoked outrage and the NPA announced it would seek a longer term.
Pistorius has always insisted the shooting was a mistake, saying he thought an intruder had entered his home and he feared for his safety.
He fired four shots through a locked toilet door, hitting Ms Steenkamp in the head, hip and arm.
Pistorius claimed in court it was only when he battered down the door with a cricket bat that he realised who was behind it.
Last month Pistorius denied “speculations” of a suicide attempt after he was treated at a private hospital in Pretoria for injuries suffered in jail.
The Olympian and Paralympian was rushed to Kalafong Hospital from his prison cell in Pretoria.