JOHANNESBURG: A South African appeals court has convicted Oscar Pistorius of murder, overturning a lower court's earlier conviction of the double-amputee Olympian on the lesser charge of manslaughter for shooting his girlfriend to death in 2013.

Justice Lorimer Leach of the Supreme Court of Appeal delivered the ruling by the five-judge appeals court Thursday in Bloemfontein and said the trial court, the North Gauteng High Court, should impose sentence.

Pistorius, 29, was earlier convicted of manslaughter, or culpable homicide, for shooting Steenkamp through a toilet door in his home early on Valentine's Day 2013.

Prosecutors said Pistorius shot Steenkamp during an argument, while the defense said Pistorius killed Steenkamp by mistake, thinking she was an intruder.

Leach said regardless of who might have behind the door, Pistorius should have known someone could be killed if he fired.

Read: Oscar Pistorius indicted on murder charge

Pistorius family's spokeswoman said that their legal team study the court verdict and the family will be guided by lawyers on the next steps to be taken.

The former track star was put under house arrest at his uncle's mansion in a Pretoria suburb on Oct. 19 after serving one year of a five-year prison sentence, in line with the guidelines of South Africa's correctional services department.

On Nov 3, prosecutors argued at the Supreme Court of Appeal, which is in Bloemfontein city, that the judge at Pistorius' murder trial in the North Gauteng High Court in Pretoria made errors when she acquitted him of murder.

The runner should have known that someone could be killed when he fired four times through the door of a toilet cubicle, according to the prosecution.

Under the concept of “dolus eventualis” in South African law, a person can be convicted of murder if they foresaw the possibility of someone dying through their actions and went ahead anyway.

Pistorius, a multiple Paralympic champion, became one of the world's most famous athletes and the first amputee to run at the Olympics and the able-bodied world championships.

He was known as “Blade Runner” for his carbon-fiber running blades.