Serena Williams survived a busted lip and Roger Federer and Andy Murray raced into round three on a day of ice-packs and sunscreen as temperatures soared at the Australian Open on Thursday.

Defending champion Victoria Azarenka toyed with the fourth "double bagel" of the women's draw as she went through 6-1, 6-0 at a scorching Melbourne Park, where the mercury nudged 41 degrees Celsius (106 Fahrenheit). The top seed thumped Eleni Daniilidou to remain on course for a semi-final with the thundering Williams, who appeared unimpeded after rolling her ankle in round one as she demolished Spanish teen Garbine Muguruza 6-2, 6-0.

But Williams did not escape unhurt as she smashed herself in the mouth with her racquet during the first set, leaving her bleeding and fearing she had lost a tooth. "I just busted it, busted it wide open," she said. "I think it happens to everyone, but I have never busted it wide open like that. So, yeah, I was like, 'Oh, no, I can't have a tooth fall out.' That would be horrible."

As tannoy announcements urged fans to seek shade, thousands donned hats and sunglasses and slathered themselves in sunscreen for the hottest day of the tournament so far. However, organisers stopped short of closing the mechanical roofs on the two main courts, the Rod Laver and Hisense arenas.

Braving the heat, US Open champion Murray maintained his Grand Slam winning streak with a quickfire 6-2, 6-2, 6-4 destruction of Portugal's Joao Sousa -- and then headed straight for the Melbourne Park ice baths. "It's tough to get used to these conditions and it was extremely tough out there, and it was good to get it done in three sets," said the Scot.

Former finalist Jo-Wilfried Tsonga booked his place in the next round with a straight-sets win over Japan's Go Soeda, and Lithuanian qualifier Ricardas Berankis stunned German 25th seed Florian Mayer. Big-serving Canadian Milos Raonic downed the Czech Republic's Lukas Rosol, and Germany's 17th seed Philipp Kohlschreiber had a straightforward win against Amir Weintraub of Israel.

France's Gael Monfils inexplicably double-faulted four times on match points before finally clinching an erratic, five-set win against Lu Yen-hsun, and sixth seed Juan Martin Del Potro beat Germany's Benjamin Becker. In the showpiece evening match, Federer blew Nikolay Davydenko away 6-3, 6-4, 6-4 to extend his record to 18-2 against the Russian, and set up an encounter with brash Australian Bernard Tomic, 20.

"It's nice he's been able to turn it around after a tough end of the year last year. It seems he's playing well," Federer said of Tomic, who won his first tour title this month. "Obviously a difficult match-up in terms of early in the tournament.

But I've got to be ready, so I'm looking forward to the match." Azarenka had watched 6-0, 6-0 whitewashes by Williams and Maria Sharapova (twice), and she was similarly dominant as she floored Daniilidou of Greece for the loss of just one game.

"I definitely stepped it up from my first match, and I was in the zone trying to execute all of my shots. I was trying to make everything happen, and that's what I'm happy about," she said. As women's seeds Roberta Vinci, Maria Kirilenko and Yanina Wickmayer joined Azarenka and Williams in the next round, Australian media howled at the defeat of Samantha Stosur, who was bundled out by Zheng Jie on Wednesday.

"Abject Stosur sinks to new depths," said The Age, while the Herald-Sun went with "Home-groan talent," adding that the "Yips are getting bigger" for Stosur after a string of failures on Australian soil. For the ninth seed, it was her sixth loss in seven matches on home soil, including last year's first-round exit at Melbourne -- which came just months after she won the US Open in New York.