Second seed Karolina Pliskova and fifth seed Elina Svitolina were high-profile casualties in the third round of the Australian Open on Saturday.

Pliskova fell to a straight-sets defeat to Anastasia Pavlyuchenkova and Svitolina was soundly beaten by two-time grand slam champion Garbine Muguruza.

Belinda Bencic and Donna Vekic were also sent packing, losing to Anett Kontaveit and Iga Swiatek respectively.

There was no sign of a slip-up from former world number one Simona Halep, however, as she made serene progress to the next round by easing past Yulia Putintseva.

PLISKOVA, SVITOLINA CRASH OUT

After defending champion Naomi Osaka and 23-time grand slam winner Serena Williams were eliminated on Friday, Pliskova joined the star duo in dropping out of the tournament.

Pliskova went down 7-6 (7-4) 7-6 (7-3) to 30th seed Pavlyuchenkova in the first match on Rod Laver Arena on Saturday.

"I think she was playing very well. Maybe the best she played against me so far in the last couple matches," Pliskova told reporters. "But let's say I was [at] about 40 per cent of my game, so of course then she can feel so much better if I just don't play enough [of] what I can play. 

"That's how it is. I think especially [in] the important moments she always served well so I had a couple chances here and there. But I think she just played better than me."

Svitolina did not fare much better as she lost to Muguruza in 67 minutes, the Spaniard - now ranked 32 in the world - hitting 31 winners to advance 6-1 6-2.

BENCIC, VEKIC SENT PACKING

It was another tough day for seeds as Bencic (6) and Vekic (19) failed to progress beyond the third round in Melbourne.

US Open semi-finalist Bencic was swept aside in just 49 minutes, humbled 6-0 6-1 by 28th seed Kontaveit on Margaret Court Arena.

"I think every grand slam there are seeded players losing, so I think this grand slam was even the best because no top-10 player lost in first round," she said in a news conference. "It's the same at every grand slam. There are upsets, and I think it's normal, because it's tennis, and tennis is very unpredictable."

Kontaveit will face Swiatek after the 18-year-old stunned Vekic 7-5 6-3.

HALEP, KERBER MOVE ON

Halep thwarted in-form Putintseva 6-1 6-4 to move through to the second week of the slam for a third consecutive year.

Fourth seed Halep - runner-up in Melbourne two years ago - needed one hour, 18 minutes to progress to the fourth round.

Away from Rod Laver Arena, 2016 champion Angelique Kerber ground out a 6-2 6-7 (4-7) 6-3 victory over Italian Camila Giorgi.

Kerber was pushed but the three-time major winner clinched a spot in the fourth round for the fifth successive season after two hours, eight minutes.

MERTENS AND BERTENS ADVANCE

Next up for Halep is 16th seed Elise Mertens, who required three sets to overcome CiCi Bellis.

Mertens was two points from victory in the second set after taking a 5-4 lead in the tiebreak but failed to close it out. However, she managed to keep her run alive by reeling off the next six games in succession.

The 2018 semi-finalist breezed through the final set to wrap up a 6-1 6-7 (5-7) 6-0 victory in just under two hours.

Joining Mertens in the next round was Dutch ninth seed Kiki Bertens, who made the second week of the Australian Open for the first time.

Bertens claimed a 6-2 7-6 (7-3) victory over Zarina Diyas and has a meeting with Svitolina's conqueror Muguruza to look forward to.