South African athlete Oscar Pistorius should be given "sufficient punishment" for killing his girlfriend Reeva Steenkamp, her cousin has told the ongoing sentencing hearing in Pretoria.

Kim Martin told the court Pistorius "needs to pay for what he has done".

The prosecution is making its case for a jail term for Pistorius, 27.

He was convicted of culpable homicide last month but cleared of murder and faces up to 15 years in jail, but the judge may suspend it or impose a fine.

The defence has argued that Pistorius should serve house arrest and community service for the killing - a suggestion branded as "shockingly inappropriate" by prosecutor Gerrie Nel.

The prosecution insists that Pistorius should go to jail, saying his negligent actions have left a "broken family".

'Not seeking revenge'

At the hearing, Ms Martin said she was fearful of Pistorius.

"My family are not people who are seeking revenge, we just feel that to shoot somebody behind a door that is unarmed, that is harmless, needs sufficient punishment," she said.

On Wednesday, Ms Martin recounted her pain at hearing that the 29-year-old South African model had been shot dead, saying her death was "the end of the world".

Ms Martin was the prosecution's first sentencing witness.

Moleko Modise, the Acting National Commissioner for Correctional Services, is the second. Mr Modise has been called to defend the reputation of South African prisons.

Mr Modise said South Africa's prisons "can cope" with disabled prisoners like Pistorius.

He said that a health assessment was conducted on all inmates "within six hours of admission", and a complete assessment would be completed within 21 days to consider the "security classification" and "social and psychological needs" of the prisoner.

Under cross-examination from defence lawyer Barry Roux, Mr Modise said he thought Pistorius should be placed in the hospital wing of a prison, not the regular section.

Mr Roux cited a report saying incidents of assault and torture in South Africa's prisons had increased over the past year.

Mr Roux also said several newspapers had reported threats made by prisoners against Pistorius. However, Mr Modise said he was not aware of any threats being made against Pistorius.

Mr Nel has said he will call three of four witnesses in all.

'Pistorius vulnerable'

On Wednesday, Mr Nel cross-examined social worker Annette Vergeer.

The defence witness had said double-amputee Pistorius should be placed under house arrest rather than sent to prison, because he would be "a lot more vulnerable than the normal man" in jail.

Mr Nel said her opinion of a sentence of house arrest plus community service "cannot be considered".

"If the court sentence is too light, and society loses trust in the court, they will take the law into their own hands," Mr Nel said.

"That's what the court has to guard against."

The Paralympic sprinter denied murdering Ms Steenkamp after a row on Valentine's Day last year, saying he shot her by mistake.

Ms Steenkamp, a law graduate, was hit three times by bullets shot through a toilet door by Pistorius at his home in the capital, Pretoria.