Champ Djokovic through at Aussie Open as violence flares

Defending champion Novak Djokovic survived a scare against Bosnian-American Amer Delic as violence flared between rival groups of fans after their match on Friday.

Bosnian-born Delic, ranked 127, shocked Djokovic when he took the second set and forced a tense fourth-set tie-break before the Serbian third seed won 6-2, 4-6, 6-3, 7-6 (7/4).

Moments after the finish, dozens of youths watching on a big screen outside at each other, leaving one woman injured, before they were thrown out.

Delic expressed his dismay at the incident, which came despite his pre-match appeal for calm and great sportsmanship shown by both players.

"I'm really sad to hear about it. As I said a couple days ago, there's absolutely no place for that here. This is a tennis match," he said.

Djokovic was reluctant to get involved, saying only that players had no control over what fans did.

"I am happy when I see that I have my own group of fans that are supporting me in a fair way, of course, not provoking my opponent and everything is going in a sportsmanship way," he said.

"I didn't know about this encounter whatever they had outside of the courts."

Djokovic, who won his only Grand Slam title here last year, is the first top-four player to drop a set but remains on course for a semi-final with three-time champion Roger Federer.

The Serb raced through the first set in 31 minutes but was flummoxed by Delic's serve and giant forehand as the underdog made it a set each.

Delic was slowed by blisters on his toe in the third set but was unbreakable in the fourth and had two set points, which Djokovic escaped with an ace and a lucky net cord.

The Serbian then came from two points down to win the tie-breaker and the match, setting up a clash with either American 23rd seed Mardy Fish or 2006 finalist Marcos Baghdatis.

"I can't play perfect tennis. It's normal to have ups and downs during the tournament and during the matches," Djokovic said.

"I played the best tournament of my life here last year, which helps me out for this year. I feel very comfortable playing on the center court.

"I proved that by today's match and two days ago. Just confident. Winning matches gives you more confidence and self-belief."

The Australian Open gained an unsavoury reputation for ethnic clashes after Serbian and Croatian fans attacked each other flagpoles, bottles and boots in 2007.

Last year, police used pepper spray to subdue rowdy elements of the crowd watching a match between Konstantinos Economidis of Greece and Chile's Fernando Gonzales.

Delic was bidding to become the first lucky loser to reach the Open's last 16. After failing to come through qualifying, he was given his chance when Germany's Nicolas Kiefer pulled out injured.