Melbourne: The Australian Open was on Friday once again the centre of ethnic violence.
Chairs were hurled around busy Garden Square and punches were thrown in the latest ugly incident.
The troublemakers had been watching Serb Novak Djokovic beat Bosnian American Amer Delic in a tight four-set match, and baiting each other.
Witnesses said the trouble erupted about 1600 HRS (IST) when a drink was thrown by someone in the crowd.
It grew into a melee involving at least 20 warring fans.
Police labelled the incident "a bit of a chair-throwing contest" and said only plastic chairs were used as missiles. But at least one metal-framed chair was hurled.
More than 30 were thrown out of Melbourne Park and escorted out of the precinct by police and security guards. Two men will be charged with riotous behaviour.
Delic later appealed to his fans to restrain themselves. He said he was "really sad" that innocent people had been injured.
Djokovic, however, declined to read the riot act to his fans. "If I start to lose my energy on these things, I'm going to lose my focus as well," he said.