Jannik Sinner of Italy plays a backhand return to Alex de Minaur of Australia during their quarterfinal match at the Australian Open tennis championship in Melbourne, Australia. (AP )

MELBOURNE, Jan 22, (Xinhua): Defending champion Jannik Sinner shrugged off health concerns with an evisceration of eighth seed Alex de Minaur on Wednesday, while women's second seed Iga Swiatek also stormed into the Australian Open semifinals.

There had been concern over Sinner's fitness after he fought through illness during his grueling fourth-round victory over 13th seed Holger Rune.

There was speculation that top seed Sinner might not take his place against de Minaur, but he dispelled those fears with 27 winners in a near-flawless 6-3, 6-2, 6-1 victory in one hour and 46 minutes.

It was a bitter disappointment for de Minaur, who was Australia's main title hope but he fell well short of his goal of becoming the country's first men's champion since Mark Edmondson in 1976.

Sinner's championship defense next goes through flamboyant American Ben Shelton, who overcame Lorenzo Sonego 6-4, 7-5, 4-6, 7-6 (4) in a high-octane contest that lasted nearly four hours.

The left-handed Shelton relied on his ferocious serve, the fastest clocked at 232kph144mph, to counter the Italian's cavalier shotmaking as he battled into his second Grand Slam semifinal.

Swiatek showed no mercy against eighth seed Emma Navarro with a 6-1, 6-2 romp in one hour and 29 minutes.

The Pole has shown no signs of being affected by the doping saga hanging over her, dropping just 14 games so far in the tournament.

She broke five times to overwhelm a flagging Navarro, who had gritted through four consecutive three-set matches, including a second-round thriller against China's Wang Xiyu.

Having previously struggled at the Australian Open by her lofty standards, Swiatek has been on a mission as she reached the final four for the second time from seven appearances in Melbourne.

Swiatek won just five games against American Danielle Collins in the semifinals in 2022.

The 23-year-old Pole moved closer to a first Australian Open title but she will first face 19th seed Madison Keys in the semifinals.

The former US Open finalist overcame a slow start to edge 28th seed Elina Svitolina 3-6, 6-3, 6-4 in one hour and 53 minutes.

The big-hitting American slammed six aces and 49 winners to finish strongly against the former world No.3.

Meanwhile, China's Zhang Shuai and Kristina Mladenovic of France fell to top seeds Taylor Townsend and Katerina Siniakova 6-1, 7-5 in the quarterfinals of the women's doubles.

The women's semifinals will be held on Thursday with defending champion Arnya Sabalenka taking on 11th seed Paula Badosa, while Swiatek meets Keys in the latter match.