Prosecutors will push for a longer sentence for Oscar Pistorius.

A prosecuting authority in South Africa have said they believe Oscar Pistorius’ six-year sentence is “disproportionate” and “shockingly too lenient” for the murder of his partner, Reeva Steenkamp.

When Pistorius was sentenced earlier this month, High Court judge Thokozile Masipa listed several reasons for giving the Olympic sprinter significantly less than the minimum 15-year term for murder. The Judge said Pistorius believed he was shooting an intruder, and maintained “he cannot be at peace.”

Many activists argued that the term was far too short, and now, the National Prosecuting Authority have released a statement indicating they will file papers to appeal the sentence on Thursday.

"The sentence of six years imprisonment, in all the circumstances, is disproportionate to the crime of murder committed [and] shockingly too lenient," read the statement.

The authority added the sentence was "an injustice and has the potential to bring the administration of justice into disrepute."

Pistorius' lawyers said earlier this month they would not appeal against the term.

Watch Oscar Pistorius recall the night of Steenkamp's murder. Post continues after video...

Prior to his sentencing, Pistorius appeared on 60 Minutes, telling his side of the story of how he came to shoot Steenkamp, a model and law graduate, in the middle of the night on Valentine's Day in 2o13. He said through tears that he truly believed she was an intruder, and assumed she was in bed throughout the ordeal.

He fired four shots through the toilet door.