South Africa's ex-Olympic runner Oscar Pistorius was released from jail on parole Friday and "is now at home", authorities said, almost 11 years after he shot dead his girlfriend Reeva Steenkamp in a crime that gripped the world.

Having served more than half his sentence, the 37-year-old double-amputee was quietly whisked out from the Atteridgeville prison on the outskirts of the capital Pretoria, avoiding the hordes of media gathered outside.

"He was admitted into the system of Community Corrections and is now at home," the department of correctional services said in a statement.

Pistorius, known worldwide as "Blade Runner" for his carbon-fibre prosthetics, will not be allowed to speak to the media as a condition of his parole.

Prison authorities had previously warned the press that there would be no opportunity to photograph or speak to him.

Pistorius killed Steenkamp, a model who was 29 years old at the time, in the early hours of Valentine's Day 2013, firing four times through the bathroom door of his ultra-secure Pretoria house.

The shooting came a year after Pistorius made history by being the first double-amputee to race at Olympic level when he appeared at the London 2012 games.

He was found guilty of murder and given a 13-year jail sentence in 2017 after a lengthy trial and several appeals.

He had pleaded not guilty and denied killing Steenkamp in a rage, saying he mistook her for a burglar.

- Therapy required -

The morning ahead of his release, Steenkamp's mother June issued a statement saying that while she accepted the decision of the justice system and conditions of his parole, "the pain is still raw and real".

"There can never be justice if your loved one is never coming back, and no amount of time served will bring Reeva back," she said.

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

Offenders in South Africa are automatically eligible for parole consideration after serving half their sentence.

Pistorius lost a first bid in March when the board found he had not completed the minimum detention period required to be let out.

The Constitutional Court in October ruled that was a mistake, paving the way for a November hearing that approved his release.

As part of his parole, until the end of his sentence in 2029, Pistorius must undergo therapy for anger and gender-based violence issues.

He will also be banned from consuming alcohol and other substances, required to complete community service and also be home at certain hours of the day.

The conditions "send out a clear message that gender based violence is taken seriously" by the country's justice system, June Steenkamp said Friday.