Andy Murray [ Images ], Serena Williams [ Images ] and Rafael Nadal [ Images ] led a charge into the fourth round of the Australian Open [ Images ] on Saturday as the focus switched back to tennis and away from ethnic clashes which had marred the "Happy Slam."

Police and security officers beefed up their presence at Melbourne [ Images ] Park after fighting between Serb and Bosnian ethnic fans on Friday and all aggression was restricted to the action on the courts.

Three-times former champion Williams coasted through with a 6-1, 6-4 win over China's Peng Shuai [ Images ] and sent an ominous reminder to her younger rivals why she remains the standard bearer of women's tennis.

"I'm feeling a little rusty, for whatever reason," Williams said. "It was definitely a lot better than my second round but I'm still trying to work on some things and hoping they'll come together."

Williams's next opponent will be Victoria Azarenka [ Images ] of Belarus, who sent former champion Amelie Mauresmo [ Images ] packing with a 6-4, 6-2 win.

Mauresmo, who won the Australian Open in 2006 when her semi-final and final opponents both retired injured, struggled to hold her serve against the in-form 19-year-old.

Azarenka broke six of Mauresmo's nine service games as she cruised to victory in 87 minutes, leaving the Frenchwoman rueing her missed opportunities.

"It's a little bit frustrating," Mauresmo said. "It's really the key points... that I didn't play good enough."

In the men's draw, British fourth seed Murray removed any doubts he was not a serious contender for the title with a 7-5, 6-0, 6-3 demolition of Austria's Juergen Melzer.

He next meets Fernando Verdasco [ Images ].

"Against Verdasco, it's very important to use my head," Murray told reporters.

"I have a very good record against left handers. The only one I've lost to on the tour has been Nadal. I need to use my head, make him do a lot of thinking and moving.

"If I play like I did tonight, I can definitely win that one."

Top seed Nadal pummelled Tommy Haas [ Images ] 6-4, 6-2, 6-2 to reach the fourth round, showing no mercy in outgunning the German who had just returned to the tour after elbow problems.

"For sure I played my best match here. I'm very happy with my level today," Nadal said in a courtside interview.

"Probably I played my one of my best matches in Australia [ Images ]."

Last year's runner-up Frenchman Jo-Wilfried Tsonga advanced comfortably enough with a 6-4, 6-2, 1-6, 6-1 win over Israel's Dudi Sela [ Images ].

Tsonga next meets ninth seed James Blake [ Images ] -- the American beat Igor Andreev of Russia [ Images ] 6-3, 6-2, 3-6, 6-1.

"Overall I was playing my kind of game: aggressive and taking time away from Igor, which I think is something you got to do," Blake said.

"If you let him set up and rip that forehand, he's going to hurt you pretty bad."

Spain's Carla Suarez Navarro [ Images ] proved her shock win over Venus Williams [ Images ] on Thursday was no fluke when she defeated compatriot Maria Jose Martinez Sanchez 6-1, 6-4.

Suarez Navarro will play another Spaniard, Anabel Medina Garrigues, in the fourth round.

Despite the bright sunshine in Melbourne it was a gloomy afternoon for the Bondarenko sisters from Ukraine.

Kateryna Bondarenko, the younger of the siblings, was crushed 6-2, 6-2 by China's Zheng Jie [ Images ] before Alona Bondarenko lost 7-6 6-4 to Svetlana Kuznetsova [ Images ], one of six Russian women through to the last 16.

World number four Elena Dementieva [ Images ] kept up the Russian charge by beating local hope Samantha Stosur [ Images ] 7-6, 6-4.

France [ Images ], attempting to get four men through to the round of 16, made a perfect start on Saturday when Gilles Simon and Gael Monfils both won in straight sets.

Simon, seeded sixth, beat Croatia's [ Images ] Mario Ancic 7-6, 6-4, 6-2 while 12th seed Monfils defeated Spain's Nicolas Almagro 6-4, 6-3, 7-5.

Richard Gasquet was unable to join his countrymen, though, as he let slip a two-set lead to fall to 13th-seeded Fernando Gonzalez [ Images ], of Chile, 3-6, 3-6, 7-6, 6-2, 12-10.

Gonzalez meets Nadal next.