MELBOURNE, Australia — Serena Williams couldn't believe what she was seeing. A nearly naked man had just run on court while she and sister Venus were playing doubles at the Australian Open, prancing around before being arrested.

"I just thought, my eyes, my innocent eyes," Williams said Saturday, still chuckling at the memory.

While it was no laughing matter for tournament officials, who have beefed up security this year and were dealing with a near-riot a half-hour later between Serbian and Bosnian fans, the incident was just a brief distraction for Williams, who said she was focused on beating Japan's Ayumi Morita and Germany's Martina Muller 6-3, 6-3.

The man, wearing only a shirt, jumped onto the court, sprinted across the sidelines and made several dance moves.

"First, I saw him jump over and then I noticed he didn't have underwear on," Williams said after her third-round singles victory over China's Peng Shuai. "I thought, `OK, I must be seeing things.'

"He ran out on the court. I was thinking, `I hope he doesn't come,' because he was pretty close to me and V. I was like, `I hope he doesn't come, he's too close.' Then I thought, `This is crazy.' Doesn't really happen too much."

As he headed toward an exit, the man was met by security guards, arrested and banned for the event. He was not immediately identified.

Australian Open officials said the streaker was on the court for 14 seconds.

"The focus of the on-court security team is always on player protection," a statement from tournament officials said. "They are instructed not to chase offenders as their focus at all times must remain on the players. The on-court actions of the security personnel reflected this focus on player protection."

The incident added to a busy day for police at the Grand Slam event, with a near-riot breaking out between Serbian and Bosnian fans after Serbia's Novak Djokovic, the defending champion, beat Bosnian-born American Amer Delic.

Police charged two men Friday, another on Saturday and were reviewing video to identify any other people who should face charges.

One woman was knocked over and dazed after being hit in the head by a chair. About 30 people were ejected from Melbourne Park.

In 2006, Wimbledon officials said they were considering the installation of security screens or fences around Center Court after two security breaches.

During Roger Federer's quarterfinal win over Mario Ancic, two men came on the court with rackets and balls, and one of them hit a shot. A day earlier, a streaker interrupted a quarterfinal match and danced and cartwheeled only 10 feet from Maria Sharapova.

Security at tournaments was increased after former No. 1 Monica Seles was stabbed in 1993 by a man who ran on court during a match in Hamburg, Germany.