Dozens of rival Serbian and Bosnian tennis fans have clashed at the Australian Open in Melbourne. The opposing supporters threw chairs and traded punches and kicks after the match between Novak Djokovic, the defending champion from Serbia, and Amer Delic, who plays for the US but was born in Bosnia. Police arrested two men and ejected another 30 people from the grounds. One woman was knocked out after being hit on the head by a chair, although police later said she had not been seriously injured. The fighting began in a garden outside the main centre court arena then flared up again outside Melbourne Park. Inspector Chris Duthie said two men had been charged with riotous behaviour and discharging a missile while another man had been fined on the spot. "The matter was dealt with very quickly and effectively by the police and we expect no more problems," he said. "We have a very effective police presence here. You can't stop everything happening but we will make sure this sort of thing doesn't happen." Before the match, Delic posted a plea on his website pleading for fans to behave and said he was disappointed when told about the fighting. He said: "I'm really sad to hear about that. As I said a couple days ago, there's absolutely no place for that here. This is a tennis match." The Australian Open has been marred by a series of violent clashes since 150 Croat and Serb fans first began brawling at the event two years ago. Two people were evicted on Wednesday after scuffling at a bar following a match between Croatia's Marin Cilic and Janko Tipsarevic of Serbia.