Violence broke out after militant ANC supporters poured out of their houses to shout insults and throw stones and bottles at DA activists, according to an AFP reporter at the scene.
Between 1,500 and 2,000 DA supporters had gathered for a campaign rally in the township -- which was at the heart of the anti-apartheid struggle -- when the incident happened.
Stewards struggled to contain the violence, with both sides coming to blows before the police stepped in.
ANC President Jacob Zuma is expected to win the May 7 elections, even though he has been forced onto the defensive recently over corruption claims related to multi-million dollar improvement works he made to his home, and for failing to drive down unemployment.
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The ANC has asked the courts to ban a text message campaign by the DA which plays on the Zuma scandal, while one of the DA's election adverts has been banned by the SABC, the national broadcaster.
The DA has accused the broadcaster of censoring the party.