Pretoria, Nov 24 (IANS): A South African court on Friday increased from six to 13 years and five months former Paralympian Oscar Pistorius's prison sentence for murdering his girlfriend, Reeva Steenkamp.

The Supreme Court of Appeal in Bloemfontein increased the prison term after prosecutors argued that the six-year term for murdering Steenkamp in 2013, reports the BBC.

Pistorius claimed he shot dead Steenkamp on Valentine's Day after mistaking her for a burglar. He fired four times through a locked toilet door at his home in the capital city of Pretoria.

Prosecutors argued that the six-year term was "shockingly light".

However, a lower court justified the six-year sentence by citing mitigating circumstances such as rehabilitation and remorse. It said they outweighed aggravating factors such as his failure to fire a warning shot.

The athlete was not in court to hear the decision.

A spokesman for Steenkamp's family said the ruling "verified there was justice", the BBC reported.

Pistorius was initially given a five-year term for manslaughter in 2014 but was found guilty of murder on appeal in 2015.

Previously, the six-time Paralympic gold medallist had made history by becoming the first amputee sprinter to compete at the Olympics, in 2012 in London, running on prosthetic "blades".

He had his legs amputated below the knee as a baby.