Oscar Pistorius' charity work in the spotlight and attacked in court during sentencing hearing
Oscar Pistorius appeal under way in South Africa Getty

Oscar Pistorius remained locked up in prison as the appeal against his sentence for killing Reeva Steenkamp got under way in Pretoria.

Locking horns in court again were prosecutor Gerrie Nel and defence lawyer Barry Roux, as both engaged in a technical argument about legal definitions.

Nel launched the state's bid to get Pistorius, 28, convicted of murder and jailed for decades by claiming the judge's verdict in the case was faulty.

He said: "If one applies the law, there is not other reasonable explanation than murder."

Defending the former paralympian, Roux said there was no legal basis for an appeal and that the state was simply "unhappy" with the outcome.

Central to the appeal was the issue of intent, known by the phrases 'dolus eventualis' and 'dolus directus.'

Nel claimed judge Thokozile Masipa was wrong to rule Pistorius did not foresee he might kill somebody, when he opened fire into the toilet cubicle at his luxury home on Valentine's Day last year.

Pistorius is serving five years for culpable homicide and has a suspended sentence for an incident in a restaurant.

Under his current sentence, he could be eligible for parole next year.

The appeal continues.