A South African court has increased Olympic athlete Oscar Pistorius's jail sentence to 13 years and five months for killing his girlfriend. Prosecutors had argued that the six-year term for murdering Reeva Steenkamp was too short.<br/><br/>The lower court had justified deviating from the prescribed 15-year sentence by citing mitigating circumstances such as rehabilitation and remorse. Pistorius claimed he shot dead Ms Steenkamp on Valentine's Day in 2013 after mistaking her for a burglar. 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.