ANC rebel Julius Malema appears in court today on corruption charges that his supporters say are politically motivated.
Police said they would close roads around the courthouse in Polokwane, the provincial capital of Mr Malema's native Limpopo, 350km north of Johannesburg, for one of the biggest trials since the end of apartheid in 1994.
"No lawlessness will be tolerated and those who break the law will be arrested immediately," a police statement said, ahead of a planned demonstration by thousands of supporters of South African President Jacob Zuma's most prominent critic and an advocate of mining nationalisation.
An arrest warrant was issued last week for the former ANC Youth League leader, with local media saying he was facing charges of fraud, corruption and money laundering in the awarding of government contracts in Limpopo.
Mr Malema was expelled by the ruling African National Congress (ANC) in April for causing rifts in the party, but he has kept up his anti-Zuma tirades, saying the polygamist president should be removed since he pays more attention to his personal life than to running Africa's biggest economy.
His supporters see him as an eventual leader of the ANC, but at 31 he is too young to replace Mr Zuma at the head of the party that has governed South Africa for nearly two decades.
The Youth League's new leaders, who still back Mr Malema, dismissed the charges as a politically motivated gambit to silence Mr Zuma's most vocal critic ahead of an ANC leadership election in December.
"State institutions must never be used to settle political scores because that will plunge the country into a banana republic and confirms our view that we are becoming a police state," they said in a statement.
Mr Malema stormed back from the political wilderness in August, blaming Mr Zuma's administration for the police killing of 34 strikers at a platinum mine on August 16th - the deadliest security incident since the end of white-minority rule.
Mr Malema's supporters, who accuse the president of trying to sideline him ahead of the ANC election, are preparing a vigil on tonight, with 15,000 people being bussed in to Polokwane, the daily Sowetan reported. The ANC establishment has condemned Mr Malema as an opportunist.
One of South Africa's best political speakers, Mr Malema rose from poverty with populist calls to seize white-owned farm land and for a government takeover of crucial sectors of Africa's largest economy.
Styling himself an "economic freedom fighter", he has revived a call for nationalisation of mines, an option so far shunned by the government because it would bankrupt the country but whose spectre unnerves investors in a sector producing about 6 per cent of national economic output.
With a penchant for expensive cars, Swiss watches and champagne parties, Mr Malema has been under investigation by the police's elite Hawks detective division for alleged corruption relating to government contracts in Limpopo. Mr Malema has also been given a bill for nearly $2 million (€1.5 million) for unpaid taxes, the South African Revenue Service said at the weekend.
Reuters