Jailed murderer and disgraced South African athlete Oscar Pistorius has been allowed to attend his grandfather’s memorial service.

According to South Africa's prison department there was nothing improper about the former Paralympian’s brief release on Tuesday to attend the memorial in Centurion in Gauteng province, the country's economic heartland.

It was “on compassionate grounds,” the department's spokesman, Singabakho Nxumalo, said.

“This concession is only granted when it concerns a direct family member [father, mother, child, spouse, brother, sister, grandfather and grandmother],” he added.

The 31-year-old double amputee was escorted to the memorial service and is currently back behind bars in the capital, Pretoria, Mr Nxumalo said.

Pistorius is serving a 15-year prison sentence for shooting dead his model girlfriend Reeva Steenkamp on Valentine’s Day 2013.