Top seeds Ash Barty and Naomi Osaka cruised into the last 16 of the China Open with straight sets victories in their second round matches in Beijing on Tuesday.

World No. 1 Barty defeated China's Zheng Saisai to progress into the quarterfinals after an encounter that lasted more than two-and-a-half hours.

Barty fired seven aces, converted four of nine break points and smashed 23 winners in a clinical display which she said was enough to get the job done.

"It was solid today without being fantastic," Barty said. "It was what we needed to do today. There were times where it was pretty good and there were times where it was challenging."

"It's a court that I think is tough to neutralize and play defense over a long period. It's definitely a court that you get your bang for buck and you get value when you try to take the initiative."

Despite her defeat, Zheng was pleased with her performance.

"Overall, I thought I played well," Zheng said. "I was getting into my game in the second set. But when it went to her service games in the third set, she served really well. That was a turning point. I lost focus. My injury had some impact on my game."

Barty will face Czech seventh seed Petra Kvitova in the quarterfinals.

Japan's Osaka, seeded fourth, needed only 59 minutes to brush aside German qualifier Andrea Petkovic with a dominant 6-2 6-0 win.

Osaka converted five break points and fired 21 winners in a one-sided contest to set up a clash with American Alison Riske, who beat Australian Ajla Tomljanovic 6-3 3-6 6-4 in the only three-set match of the day.

Teenage U.S. Open champion Bianca Andreescu reached the last 16 with a 6-3, 7-6 (7/5) victory over Belgium's unseeded Elise Mertens.

On men's side, exhausted Andy Murray battled into a singles quarterfinal for the first time in a year on Wednesday - and then immediately grabbed a snooze.

The former world No. 1 outlasted fellow Briton Cameron Norrie 7-6 (8/6), 6-7 (4/7), 6-1 over nearly three grueling hours in hot and hazy Beijing.

The 32-year-old, now ranked a lowly 503, will play top seed Dominic Thiem in the last eight of the China Open on Friday.

On the mend after a career-saving hip operation in January, Murray looked all in afterwards, and walked gingerly in and out of the post-match press conference.

Blowing out his cheeks several times, the three-time Grand Slam champion said he had slept in the 90 minutes between his victory and talking to reporters.

"I'm tired, I just had a sleep before coming. I mean, I'm really tired," he said.

To save his creaking body from more punishment, Murray said that he switched tactics in the deciding third set.

"I decided if I want to win I have to go and take risks and come to the net, try and finish the points quicker, which I did," he said.

Also into the quarterfinals was Russian fourth seed Karen Khachanov, a 7-6 (7/0), 7-6 (7/5) winner over France's Jeremy Chardy. He faces the Italian Fabio Fognini.

(With input from agencies)