Oscar Pistorius the South African Olympic and Paralympic athlete who killed his girlfriend, Reeva Steenkamp, by firing four bullets through a closed toilet door, has been sentenced to a lower than expected six years in prison.

Pistorius was freed from prison in the South African capital Pretoria last October after serving one year of a five-year term for culpable homicide the equivalent of manslaughter.

Judge Thokozile Masipa, whose sentence at the initial manslaughter trial was criticized by women's groups as too lenient, said she had accepted the defense argument that a lesser punishment was appropriate.

"Public opinion may be loud and persistent but it can play no role in the decision of this court," Masipa said.

"I am of the view that a long term in prison will not serve justice." Pistorius, who stood impassively as the sentence was read out, hugged members of his legal team and chatted briefly with his sister Aimee before being led away by police.