In this file photo taken on Jan 20, 2022, Britain's Emma Raducanu leaves the court after losing to Montenegro's Danka Kovinic in their women's singles match on day four of the Australian Open tennis tournament in Melbourne. (MARTIN KEEP / AFP)

INDIAN WELLS - Petra Martic kept her composure in a seesaw battle with Emma Raducanu on Sunday to advance to the Round of 16 with a hard-fought 6-7(3) 6-4 7-5 win at Indian Wells.

Raducanu was outstanding in the first set tiebreak, spraying winners around the court, but her energy and service speed dipped in the second set as she appeared to struggle with some physical discomfort and Martic took advantage to level the contest.

Emma Raducanu was outstanding in the first set tiebreak, spraying winners around the court, but her energy and service speed dipped in the second set as she appeared to struggle with some physical discomfort and Martic took advantage to level the contest

The 11th-seeded US Open champion Raducanu bounced back in the third and was serving for the match at 5-4 but the Croatian stepped up her defence to break the British teenager.

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Raducanu sent a forehand long on match point to end the marathon, two-hour and 46-minute contest under sunny desert skies on Stadium One.

"I'm happy that I stayed calm when I was not playing so good," Martic said in an on-court interview.

"I think the match was up and down from both sides. We both had some good periods and bad ones out here, so I'm happy I was able to let that go and just focus on the next point."

The win was Martic's first over a top 20 opponent since 2019.

In the evening session, 2015 champion Simona Halep defeated Coco Gauff 6-3 6-4 to reach the second week.

Gauff, who turned 18 on Sunday, had no answer for the Romanian veteran's superb shotmaking on a blustery night on Stadium One.

"I'm not scared about the wind. I never have been, even when I was a kid," Halep said.

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"I think I played smart tonight because from one side you had to play different, from the other side a little bit different. So I think I managed very well all the moments."

USA's Coco Gauff competes against Greece's Maria Sakkari during their quarter-final match of the 2022 WTA Qatar Open in Doha, on Feb 4, 2022. (KARIM JAAFAR / AFP)

Wearing a ribbon with the colors of the Ukrainian flag, German Angelique Kerber beat Daria Kasatkina 6-2 6-1 and said she tried to put the fact that she was playing against a Russian out of her mind.

"Right now, there's much more important issues in the world," Kerber told reporters.

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"People are fleeing, the whole situation is topic number one and is frightening for everyone. As I've said, I don't live far from the situation.

"My grandparents are there and so of course you're checking the news every five minutes or every hour, you're in touch with folks. I think right now that's the topic that is occupying my mind and everyone else here."

Next up for Kerber is a third round showdown with third seed Iga Swiatek, who defeated Clara Tauson earlier in the day.