Naomi Osaka has apologised for "disrespecting" Sorana Cirstea in her post-match on-court interview after she received a frosty handshake and a telling-off from the Romanian.

After wrapping up a 6-3 4-6 6-2 win against Cirstea in the Australian Open second round, a smiling Osaka made her way to the net to carry out the post-match formalities.

But Cirstea gave a brief handshake before exchanging some words with the Japanese 16th seed by the umpire's chair.

Asked in her on-court interview what it took to get past Cirstea, Osaka said: "Apparently a lot of 'come ons' that she was angry about."

The interviewer then asked if Cirstea was complaining because she could hear Osaka trying to pump herself up between the Romanian's first and second serves.

"I think so, but like, she could have asked me. I'm sorry," former world number one Osaka replied.

"She's a great player. I think this was her last Australian Open, so sorry she was mad about it."

In a later news conference, Osaka apologised for some of her post-match comments towards Cirstea, who is retiring from tennis at the end of the 2026 season after 20 years on the WTA Tour.

"I'm a little confused. I guess that emotions were very high for her. I also want to apologise," the four-time major winner said.

"I think the first couple of things that I said on the court were disrespectful. I don't like disrespecting people. That's not what I do."

However, Cirstea said there was "no drama" between herself and Osaka.

"It was just a five-second exchange between two players that have been on a tour for a long time. It stays between us," Cirstea, 35, said.

"Look, this is my last Australian Open. I have been playing for 20 years. It's more going on than a five-second discussion at the end that I had with Naomi."

Before the match, Osaka arrived on court in a toned-down version of her jellyfish-inspired outfit that stunned spectators on Tuesday.

She chose not to wear the white hat and veil again and also arrived without the white umbrella - but that did not stop some fans in the stands trying to imitate the already-iconic look.

"This is just something fun that I like to do on the court," Osaka said of her outfit.

"I don't really talk that much, but I like to express myself through clothes and I'm really glad that you guys loved it."

Osaka is hoping to reach the fourth round of the Australian Open for the first time since she won the tournament for a second time in 2021.

She will face Australian qualifier Maddison Inglis in the third round after the world number 168 beat Germany's Laura Siegemund.

Bencic stunned by Czech teenager

Czech teenager Nikola Bartunkova caused the biggest upset of the tournament so far when she knocked out 10th seed Belinda Bencic.

Making her debut in a Grand Slam main draw, Bartunkova fell to her knees after she recovered from a second-set bagel to wrap up a remarkable 6-3 0-6 6-4 victory over the Swiss former Olympic champion.

Suffering her first defeat of the season after six successive wins, Bencic becomes the highest seed to fall in the women's draw.

Bartunkova will hope to cause another shock when she faces Belgium's 21st seed Elise Mertens in the third round.

Elsewhere on Thursday, defending champion Madison Keys claimed a 6-1 7-5 win over fellow American Ashlyn Krueger, while American sixth seed Jessica Pegula required just 58 minutes to beat her doubles partner McCartney Kessler 6-0 6-2.

Second seed Iga Swiatek continued her bid to make history and complete the career Grand Slam with a comfortable 6-2 6-3 win over Czech Marie Bouzkova.