South Africa's former president Jacob Zuma is receiving medical treatment in Russia, a day after the country's highest court upheld a ruling that he should return to prison.

"Zuma travelled to Russia last week for health reasons, and he will be returning to the country once his doctors have completed their treatment," his spokesperson Mzwanele Manyi said in a statement on Friday.

Manyi added that the trip "was private, it was not a secret," after the information was published by local media.

On Thursday, the constitutional court upheld a ruling that Zuma should return to prison to complete a 15-month term for contempt of court. The court ruled that his release in 2021 after serving just two months of the sentence was unlawful.

Legal advice

It was not immediately clear whether he would return to custody. Prison authorities said they were studying the judgement and would seek legal advice.

Zuma served as president from 2009 to 2018 before being forced out due to corruption allegations.

He was sentenced in June 2021 after refusing to testify before a panel probing financial sleaze and cronyism under his tenure. He was then freed on medical parole, a decision that was overturned and has now been confirmed.

He faces separate charges of corruption in an arms procurement scandal dating to the late 1990s, when he was vice president.

Last week, the former head of state attended a conference on carbon credits in Zimbabwe, where he announced a donation of seven million credits for the country's new market, on behalf of a Belarusian company.