An announcement from South Africa's Department of Corrections on Friday morning indicated corrections officials had released the double-amputee Olympic and Paralympic athlete from the Atteridgeville correctional centre in the capital Pretoria in the early hours.

Pistorius has served nearly nine years of his 13 years and five months murder sentence for killing Reeva Steenkamp on Valentine's Day in 2013. The 37-year-old was approved for parole in November.

Serious offenders in South Africa are eligible for parole after serving at least half their sentence.

Pistorius is expected to initially live at his uncle's mansion in the upscale Pretoria suburb of Waterkloof, where he lived during his murder trial and where he was held on house arrest for a period in 2015-2016.

Steenkamp's mother, June Steenkamp, said in a statement she had accepted Pistorius' parole as part of South African law.

She said: "Has there been justice for Reeva? Has Oscar served enough time? There can never be justice if your loved one is never coming back, and no amount of time served will bring Reeva back.

"We who remain behind are the ones serving a life sentence.

"With the release of Oscar Pistorius on parole, my only desire is that I will be allowed to live my last years in peace with my focus remaining on the Reeva Rebecca Steenkamp Foundation, to continue Reeva's legacy."

Pistorius will live under strict conditions until the remainder of his sentence expires in December 2029, the Department of Corrections said.

It emphasised that the multiple Paralympic champion's release — like every other offender on parole — does not mean that he has served his time.

Some of Pistorius' parole conditions include restrictions on when he is allowed to leave his home, a ban on consuming alcohol and orders that he must attend programmes on anger management and on violence against women. He will have to perform community service.

Pistorius will also have to regularly meet with parole officials at his home and at correctional services offices, and will be subjected to unannounced visits by authorities.

He is not allowed to leave the Waterkloof district without permission and is banned from speaking to the media until the end of his sentence.

He could be sent back to jail if he is in breach of any of his parole conditions.

South Africa does not use tags or bracelets on paroled offenders so Pistorius will not wear any monitoring device, Department of Corrections officials said.

He will be constantly monitored by a department official and will have to inform the official of any major changes in his life, such as if he wants to get a job or move to another house.

Pistorius has maintained that he shot Steenkamp, a 29-year-old model and law graduate, by mistake.

He testified that he believed Steenkamp was a dangerous intruder hiding in his bathroom and shot through the door with his licensed 9mm pistol in self-defence.

Prosecutors said he killed his girlfriend intentionally during a late-night argument.

Pistorius was first convicted of culpable homicide — a charge comparable to manslaughter — and sentenced to five years in prison for killing Steenkamp.

After appeals by prosecutors, he was ultimately found guilty of murder and had his sentence increased, although that judgment by the Supreme Court of Appeal still did not definitively rule that he knew it was Steenkamp behind the toilet door.

Pistorius, known as the 'Blade Runner' due to his carbon fibre prosthetic running blades, was a figurehead of Paralympic sport, having won six gold medals across three Games.

He became the first amputee runner to compete in an Olympics at London 2012, when he made the semi-final of the 400 metres.