MELBOURNE--Novak Djokovic and Serena Williams made it look easy at the Australian Open Thursday as Wimbledon champion Petra Kvitova flirted with disaster.

Defending champion Djokovic thumped Colombia's Santiago Giraldo and Williams brought up her 500th career win, against Barbora Zahlavova Strycova, to reach the third round.

Former champion Maria Sharapova made it two wins for the loss of just two games, and 2008 French Open winner Ana Ivanovic also strolled through to the weekend fixtures.

Second seed Kvitova had a trickier assignment against battle-hardened Carla Suarez Navarro, but she survived a mid-match meltdown to progress in three sets—and stay on course for the top world ranking.

Djokovic has been in commanding form at the year's first major as he bids to repeat last season's astonishing haul of three grand slams among 10 titles, with a 41-match winning streak along the way.

And the Serb expended little energy in his 6-3, 6-2, 6-1 hit-out against Giraldo as he speeds towards an expected semi-final with Andy Murray, his victim in last year's final, who plays later.

Williams's victory kept up her record of reaching the third round in all but one of her 47 grand slams—despite a heavy fall late in the match on her recently injured ankle.

Resurgent Sharapova, the 2008 winner, made light of her total lack of competitive tennis this year as she thrashed US qualifier Jamie Hampton 6-0, 6-1, after dispatching Giselo Dulko by an identical score in the first round.

Afterwards, the Russian said being world number one—which she could achieve at the end of this tournament, along with Kvitova, Victoria Azarenka and the current incumbent, Caroline Wozniacki—was not her priority.

"My goal is to be ready for the important ones, for the big ones (tournaments)," said Sharapova, 24. "That's what matters at this stage in my career to me. I try to prepare as best as I can for them."

Former finalist Jo-Wilfried Tsonga went through in straight sets against Ricardo Mello but fifth-seeded baseliner David Ferrer, who reached the semis last year, needed five to beat American Ryan Sweeting.

Canada's Milos Raonic wielded his huge serve as he downed Germany's Philipp Petzschner 6-4, 5-7, 6-2, 7-5.