Six-time Paralympic champion Oscar Pistorius has been sentenced to six years in prison for the murder of his girlfriend Reeva Steenkamp.

State prosecutors called for a minimum sentence of 15 years, but Judge Thokozile Masipa told the court in Pretoria on Wednesday that there were "substantial and compelling reasons" to give a lesser sentence.

Masipa claimed that a long-term imprisonment would not serve justice, citing that there is a continued misconception that Pistorius intended to kill Steenkamp.

The double amputee has already served one year behind bars, meaning that he has five years left on his sentence, but there could be an appeal by the state if it deems the ruling too lenient.

In the initial trial, Judge Masipa found the accused guilty of culpable homicide (manslaughter) and acquitted him of murder, sentencing the athlete to five years' imprisonment.

Pistorius was given early release and transferred to house arrest at his uncle's home in Pretoria, but after an appeal by the state, his conviction was changed to murder.

The Paralympian killed his girlfriend in the early hours of Valentine's Day three years ago by firing four shots through a toilet door at his home in Pretoria.

Pistorius maintains that he mistook Steenkamp for an intruder when he fired the gun.