Australian Open PHOTOS: Djokovic, Serena sizzle; Li Na survives

Novak Djokovic's bid for a fourth successive title at Melbourne Park shifted up a gear with an impressive 6-3, 6-3, 7-5 win over Uzbek Denis Istomin on Friday. It gave the Serb a place in the Australian Open fourth round.

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The second seed was a model of controlled aggression under the lights of Rod Laver Arena, punishing Istomin's lack of court speed before picking him off with 31 crisp winners.

With new coach Boris Becker watching from the player's box, Djokovic was ruffled when broken for the first time serving for the match at 5-4 and threw a few icy stares at a rowdy pocket of fans.

But he roared in triumph after breaking back immediately and closed it out on the second match point when Istomin pushed a shot wide.

Djokovic will play Italian 15th seed Fabio Fognini for a place in the quarter-finals.

Serena Williams powered past Daniela Hantuchova 6-3, 6-3 to advance to the fourth round.

The World No 1 had lost their only other encounter at Melbourne Park in the third round in 2006 when the Slovakian beat her in straight sets, but she made no mistake this time around. 

The American, seeking her sixth Australian Open title, will now meet 14th-seeded Serbian Ana Ivanovic, who beat Australian 17th seed Samantha Stosur 6-7(8), 6-4, 6-2.

Third seed David Ferrer smashed a racket after losing his serve in the second set but recovered his composure to reach the fourth round with a 6-2, 7-6 (7-5), 6-2 victory over Jeremy Chardy.

Playing in temperatures of 42 degrees Celsius (108 Fahrenheit) on Rod Laver Arena, Ferrer's trademark brand of attritional tennis simply wore down the Frenchman, who made 51 unforced errors, in two hours and 12 minutes.

The 31-year-old Spaniard, twice a semi-finalist at Melbourne Park, took his frustrations on his racket in the second set but saved two set points to win it in the tiebreak.

He reached the fourth round for the fourth year in a row when he broke Chardy's serve for the fifth time and next meets German Florian Mayer, who earlier upset Pole Jerzy Janowicz 7-5, 6-2, 6-2 to become the first man to reach the fourth round.

Fourth seed Li Na saved a match point before rallying past a combative Lucie Safarova to record a 1-6, 7-6, 6-3 third round victory and avoid becoming the highest-ranked casualty in the first week of the Open.

Li initially appeared out of sorts as the 26-year-old Czech attacked her forehand and serve, resulting in a slew of errors from the Chinese No 1, who remained committed to her aggressive style even when she was playing badly.

Safarova, who has never beaten a top-10 opponent in a WTA Tour event, served for the contest in the ninth game of the second set and held a match point in the 12th before Li held, then produced a remarkable tiebreak that she clinched 7-2 to send it into a decider.

The 2011 French Open champion and Safarova continued to punch and counter punch in an entertaining third set before Li broke in the eighth game and then held serve to set up a fourth round clash with Russia's Ekaterina Makarova.

Seventh seed Tomas Berdych silenced a boisterous crowd on Hisense Arena as he comfortably advanced to the fourth round with a 6-4, 6-2, 6-2 victory over Bosnia's Damir Dzumhur.

The 21-year-old Dzumhur has enjoyed vocal support from Melbourne's large expatriate Balkan population in his progress throughout the tournament from qualifying.

Dzumuhur beat Croatia's Ivan Dodig in the second round in a noisy encounter on Wednesday and had been seeking to be the first qualifier to reach the fourth round at the Australian Open since Canada's Milos Raonic in 2011.

Berdych, however, was simply too strong for the youngster and gave him nothing to capitalise on, ruthlessly snuffing out his two break point opportunities to advance to a fourth round against either South Africa's Kevin Anderson or Edouard Roger-Vasselin of France.