MELBOURNE - Five-time Grand Slam champion Iga Swiatek and men's top seed Jannik Sinner had contrasting second round victories on Thursday as Chinese women's players Wang Xiyu, Zhang Shuai and Wang Yafan crashed out of the Australian Open.

US Open finalist Taylor Fritz and women's fourth seed Jasmine Paolini were also among the winners on day five.

But fifth seed Daniil Medvedev was a shock casualty after he fell to American 19-year-old Learner Tien in a near five-hour marathon that finished at almost 3am.

After letting a match point slip in the third set tiebreak, Tien finally prevailed 6-3, 7-6 (4), 6-7 (8), 1-6, 7-6 (7).

Three-time finalist Medvedev was pushed to five sets for the fifth time in his last seven matches in Melbourne as Tien claimed the biggest victory of his career.

Swiatek has barely broken a sweat so far in Melbourne and she continued to make light work of her opponents after thrashing world No 49 Rebecca Sramkova 6-0, 6-2 on Rod Laver Arena.

The second seed has seemingly not been affected by her doping saga as she strives for an elusive Australian Open title.

She has an intriguing third round clash against 2021 US Open champion Emma Raducanu, who beat Amanda Anisimova 6-3, 7-5.

"I felt really solid today and it was a really efficient game," said Swiatek, who in last year's tournament was stunned in the third round by Linda Noskova. "I'm happy that I kept my focus."

Paolini only lost five games against Renata Zarazua to set up a high-profile third round match with 28th seed Elina Svitolina.

Former Wimbledon champion Elena Rybakina beat 17-year-old American wildcard Iva Jovic 6-0, 6-3 and will next play Ukrainian 32nd seed Dayana Yastremska.

There are no more men's or women's Chinese players left in the singles competitions.

A day after China's leading player Zheng Qinwen was bundled out of the tournament, Wang Xiyu fell agonizingly short of an upset after losing to eighth seed Emma Navarro in two hours and 11 minutes.

ALSO READ: Zhang, Machac win men's doubles first round at Australian Open

Navarro, a semifinalist at last year's US Open, won 6-3, 3-6, 6-4 and will play former world No 2 Ons Jabeur in the third round.

"I was able to find something at the end, it was really tough," Navarro said.

Zhang's resurgence ended at the hands of 24th seed Yulia Putintseva after she made 32 unforced errors.

Moscow-born Kazakh romped to a 6-2, 6-1 victory and will next play Daria Kasatkina, who defeated Wang Yafan 6-2, 6-0.

The 64th ranked Wang was left to rue missed opportunities after failing to convert all seven of her break points.

Men's defending champion Sinner had an early scare against Australian wildcard Tristan Schoolkate before surging back 4-6, 6-4, 6-1, 6-3 on Rod Laver Arena in the night session.

He dropped a set for the first time in 14 matches before overwhelming 173rd ranked Schoolkate to record his 16th consecutive victory.

"It's always tough to play against a player I don't know very well," said Sinner, who next faces Marcos Giron. "I felt like he was serving really well, playing much better in the beginning than I was."

An unstoppable Fritz eased past Chilean qualifier Cristian Garin 6-2, 6-1, 6-0 in 82 minutes.

The American will next battle French veteran Gael Monfils as he continues his quest for a maiden Grand Slam title.

"He's a great guy. Just won a title, super happy for him and he's played really well in his last two matches, so it's going to be tough," Fritz said of 38-year-old Monfils, a former world No 6 and crowd favourite.

Eighth seed Alex de Minaur, Australia's title hope, blasted American qualifier Tristan Boyer 6-2 6-4 6-3 in front of a boisterous crowd and next faces world No 32 Francisco Cerundolo on Saturday.

"I'll be ready for a battle," he said. "It will be tough. He is a quality opponent, lots of firepower, great forehand.

"He has taken some big scalps and hopefully I am not the next one."

Defending champion Arnya Sabalenka will headline women's third round action on Friday, while third seed Coco Gauff has an intriguing match against 30th seed Leylah Fernandez.

READ MORE: Exit brings Down Under feeling

Men's second seed Alexander Zverev, 10-time tournament winner Novak Djokovic and four-time Grand Slam winner Carlos Alcaraz will also be striving to reach the last 16.