High Court judge Thokozile Masipa listed several mitigating factors for sentencing him to less than half the minimum 15-year term for murder, including the athlete's claim he believed he was shooting an intruder.

"The sentence that I impose on the accused... is six years imprisonment," she said.

Pistorius, 29, hugged his family before being taken out of the court in Pretoria to begin serving his term.

The double-amputee Olympic and Paralympic sprinter was freed from prison last October after serving one year of a five-year term for culpable homicide -- the equivalent of manslaughter.

But an appeals court upgraded his conviction to murder in December.

Pistorius shot Steenkamp, a model, in the early hours of Valentine's Day in 2013, saying he mistook her for a burglar when he fired four times through the door of his bedroom toilet.

The sentencing may not be the end of the saga, as Pistorius or the state could launch a final round of appeals against the length of the prison term.