Fourth seed Elina Svitolina ended the first Grand Slam odyssey of 15-year-old Marta Kostyuk in straights sets on Friday.

The Ukrainian world number four breezed past her compatriot 6-2, 6-2 in just 59 minutes on a searing day on Rod Laver Arena.

“It’s very special for me to get past the third round,” said Svitolina, who will be in the last 16 for the first time in Melbourne where she will face another qualifier, Denisa Allertova.

“It’s sad I was playing another Ukrainian girl.”

Kostyuk had been labelled the “future of tennis” by some observers after becoming the youngest Australian Open second-round winner since “Swiss Miss” Martina Hingis in 1996.

Kontaveit ousts seventh seed Ostapenko

Estonia’s Anett Kontaveit shrugged off a torrid second set meltdown to knock seventh seed Jelena Ostapenko out of the Australian Open on Friday.

The Estonian 32nd seed is into the last 16 at Melbourne Park for the first time after winning a rollercoaster match against the French Open champion 6-3, 1-6, 6-3.

“It was tough. she played so aggressive,” said Kontaveit after winning in an hour and 53 minutes.

Wozniacki advances to last 16

World No 2 Caroline Wozniacki kept her bid for a first Grand Slam title on course as she stormed into the last 16.

The second seed only scraped through to the third round by the skin of her teeth, saving two match points at 5-1 down in the third set against 119th ranked Jana Fett.

But on Friday she gave her most assured performance of the tournament so far, cruising past Kiki Bertens of the Netherlands 6-4, 6-3 in an hour and 26 minutes.

She next faces 19th seed Magdalena Rybarikova of Slovakia for a place in the quarter-finals.

Birthday girl Martic reaches last 16

Petra Martic celebrated her 27th birthday Friday by holding off a gritty challenge from Thai qualifier Luksika Kumkhum to reach the last 16 of the Australian Open for the first time.

Martic battled fierce heat and a succession of powerful winners from her opponent to prevail 6-3, 3-6, 7-5 after two hours and 10 minutes on Rod Laver Arena.

World number 81 Martic has reached three other Grand Slam fourth rounds but was made to battle all the way to get to her first in Australia.

She will face Belgium’s Elise Mertens or Alize Cornet of France for a place in the quarter-finals.

Mertens downs distressed Cornet

Elise Mertens reached the fourth round of the Australian Open in straights sets Friday after a dramatic match in which her opponent Alize Cornet needed a doctor.

Belgian world number 37 Mertens won 7-5, 6-4 in just over two hours of energy-sapping tennis on Hisense Arena as temperatures touched 40 Celsius (104 Farenheit).

“It’s hot,” said the in-form Mertens, who is coming off a successful title defence at Hobart last week and is now into the last 16 of a Grand Slam for the first time. “The toughest I have had.”

Rybarikova survives scare to make last 16

Magdalena Rybarikova, the number 19th seed, fought back after a second-set wobble to reach the last 16.

The Slovakian beat Ukraine’s Kateryna Bondarenko 7-5, 3-6, 6-1 in just over two hours on Margaret Court Arena.

She will face second seed Caroline Wozniacki or Dutch 30th seed Kiki Bertens for a place in the quarter-finals.

Suarez Navarro rallies past Kanepi to reach last 16

Spain’s Carla Suarez Navarro powered from a set down against Kaia Kanepi to advance to the last 16 with a 3-6, 6-1, 6-3 win.

The world number 39 dropped the first set in 38 minutes against her experienced opponent who is 40 places below her in the world rankings.

But she took the match by the scruff of the neck in racing through the second set in 26 minutes against the 32-year-old Estonian who was making her maiden third-round appearance at Melbourne Park.

The third set was a tighter affair but Suarez Navarro always looked in control from the back of the court as she closed out the match in an hour and 43 minutes.

The Spaniard made the quarter-finals at Melbourne Park two years ago but to match that effort looks likely next to have to get past the French Open champion Jelena Ostapenko, who plays 32nd seed Anett Kontaveit later.

Women’s singles 3rd round results:-

Petra Martic (CRO) bt Luksika Kumkhum (THA) 6-3, 3-6, 7-5

Denisa Allertova (CZE) bt Magda Linette (POL) 6-1, 6-4

Elise Mertens (BEL) bt Alize Cornet (FRA) 7-5, 6-4

Elina Svitolina (UKR x4) bt Marta Kostyuk (UKR) 6-2, 6-2

Magdalena Rybarikova (SVK x19) bt Kateryna Bondarenko (UKR) 7-5, 3-6, 6-1

Carla Suarez (ESP) bt Kaia Kanepi (EST) 3-6, 6-1, 6-3

(with inputs from AFP)