Oscar Pistorius' prison sentence for murdering his girlfriend Reeva Steenkamp has been increased to 13 years and five months by a South African court.

The Olympic and Paralympic sprinter was sentenced to six years in jail in July 2016 for shooting Ms Steenkamp dead on Valentine's Day three years earlier.

Pistorius was initially given a five-year sentence after being convicted of culpable homicide before the conviction was upgraded to murder last year.

Prosecutors argued that he should have been given a longer prison term and they got their wish, as his sentence was more than doubled in a Supreme Court of Appeal judgement on Friday. 

Pistorius was given a 15-year sentence - the minimum term for murder in South Africa - minus the time he has already served.

The 31-year-old has always maintained that he shot Ms Steenkamp by mistake, believing her to be an intruder at his home.