South Africa's heated election campaign escalated into violence Wednesday, as Johannesburg police fired rubber bullets and stun grenades to stop armed supporters of the ruling ANC from attacking an opposition rally.
African National Congress activists hurled Molotov cocktails and bricks at police and members of the Democratic Alliance (DA) who held a march for jobs near the ANC's headquarters in the city centre.
Police responded with force and formed a human barrier between supporters of the rival parties and arrested four people for public violence.
"The march was fairly peaceful until our members were pelted with stones and petrol bombs" from the ANC side, said police spokesperson Katlego Mogale.
The DA march had been planned as part of campaigning in the run-up to May 7 elections, which are expected to be the most competitive since the advent of democracy in 1994.
Ahead of the march, the ANC called the planned route a reckless provocation and a declaration of war against the ruling party's headquarters.
After failing to have the march banned in court, the ANC set the stage for a showdown by bussing in thousands of its own supporters for a rival rally.
DA supporter Mellisa Cohen said the planned march was meant to be peaceful.
"We are here to make our voice heard and we are met with violence. It's not right, especially in a democratic country," she said.
"We all have a right to express ourselves. This is barbaric."
The DA was mainly a party of white South Africans but it has been transformed over the past four years into a multi-racial group. The party has become an alternative for black voters disgruntled with the ANC.
But within the ANC camp there was anger that the DA's white leader Helen Zille was invading their turf.
"Who the hell is Zille to come and tell us how we must rule our own country? We are here to stop them," said 30-year-old Lucky Tindane.
Gripping a brick painted with the letters "DA" 20-year-old ANC supporter Kamogelo promised violence as the DA marchers approached.
"There's no toyi toyi (demonstration) without violence. There's a lot to happen here, there's a lot. We are ready for DA," he said.
Even before Wednesday's unrest the run-up to May's vote has been overshadowed by violent demonstrations about the lack of basic services and jobs.
The election -- South Africa's fifth since apartheid ended-- will be the first in which "born free" citizens can vote.
It will also be the first election since the death of Nelson Mandela, the nation's anti-apartheid hero and first democratically elected president as well as the ANC's talismanic leader.
It promises to be the sternest test yet of his party's performance during 20 years in government.
The ANC's reputation has been sullied by pervasive inequality, joblessness, cronyism and corruption.
Out of a working age population of 35 million only 15.2 million South Africans are actually employed.
Both major parties have made a promise to create jobs a key plank of their manifestos.
The ANC is widely expected to extend its hold on government in the upcoming election, but the Democratic Alliance hopes to chisel away at its support and perhaps win control of key provinces and wards.