(AFP) - South Africa's graft-tainted ex-leader Jacob Zuma is receiving medical treatment in Russia, his spokesman said Friday, 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," the 81-year-old's spokesman Mzwanele Manyi said in a statement.

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

"He will be returning to the country once his doctors have completed their treatment," Manyi said.

On Thursday, the consitutional court upheld a ruling that Zuma should return to prison to complete a 15-month term for contempt of court, dismissing an appeal seeking to keep him out of jail.

However, 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 by graft scandals.

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 just two months into his term, 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.

The former head of state last week 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.

Belarus is a Russian ally that is often described as Europe's last dictatorship -- the leaderships of both nations are targeted by Western actions.

Zuma is one of the generation of anti-apartheid fighters whose cause was supported by the Soviet Union and who retain political or personal links with Moscow.

© Agence France-Presse