Pistorius' request for compassionate leave was granted as he was classified low risk and because of his good behaviour, said spokesperson, Manelisi Wolela.

The former Paralympian was taken to the funeral at 08:00 and was returned to his prison cell by 12:00 by an elite security unit of the department.

Wolela said the request for leave was processed in accordance with departmental policy on the amenities of inmates.

"The policy details a number of privileges for offenders and it was introduced primarily to encourage offenders toward good behaviour, to instil a sense of responsibility in them and to ensure their interest and co-operation in the corrections and social reintegration programmes, while ensuring that public safety is not compromised," he said.

According to Netwerk24, Pistorius' grandmother Gerti died on Saturday, October 8. No further details were immediately available on the cause of death.

Pistorius was originally sentenced to five years for culpable homicide for killing his girlfriend Reeva Steenkamp in the early hours of Valentine's Day on February 14, 2013.

In November 2015, the Supreme Court of Appeal overturned his culpable homicide conviction and, finding in favour of the State, replaced it with murder. He had to be placed on bail again and the conditions were even stricter than his correctional supervision conditions.

He was eventually sentenced to six years in prison. The State is currently attempting to appeal the sentence.

- News24.com