The grave of anti-apartheid hero Chris Hani has been vandalised, days after a South African court ordered the far-right gunman who killed him to be released on parole, city officials said on Tuesday.

The city of Ekurhuleni, where the tomb and memorial site of the late Communist Party leader are located, said the authorities had opened an investigation.

"The monument was vandalised on Saturday night. One of the pillars is badly damaged, one side just fell off. And the electric lighting system was stolen," Ekurhuleni spokesman Zweli Dlamini told AFP.

The monument comprises four marble columns symbolising the pillars of the struggle against white rule led by the African National Congress (ANC), the party of Nelson Mandela.

Hani, a hugely popular figure and fierce opponent of the apartheid regime, was shot dead in the driveway of his house in 1993, only a year before South Africa's first multi-racial elections.

The shooting occurred just as negotiations to end apartheid were entering their final phase, stoking tensions that some feared would erupt into civil war.

Last week, South Africa's top court controversially ordered the release on parole of Janusz Walus, the Polish immigrant who shot Hani dead.

RTL

Killer: Janusz Walus / © AFP/File

Walus, 69, has served nearly three decades of a life sentence for the murder.

The decision, which Hani's widow described as "diabolical", has led to protests by the ruling ANC, and the South African Communist Party (SACP).

In a joint statement with trade unions, the two parties condemned the vandalisation of Hani's memorial as a "provocative attack."

They said it came in the context of a judgment that "pleased unrepentant apartheid perpetrators."

On Monday, the home affairs announced Walus would have to serve his parole in South Africa, saying he should not be allowed to return home to Poland given the "heinous crime committed."