Naomi Osaka beat Petra Kvitova 7-6 (7-1) 4-6 6-4 in a gruelling opening match of the WTA Finals in Shenzhen, which lasted two hours 39 minutes.

Japan's world number three Osaka won the first-set tie-break after Kvitova missed three break points at 4-4.

But the Czech, 29, fought back from a break down to take the second set and force a decider.

Kvitova made Osaka wait for her win, breaking the 22-year-old when she served for the match at 5-2.

"For me it was very difficult and usually there's first-round first jitters and you can't really afford it as she came hard at me from the beginning," Osaka said.

The WTA Finals event sees the world's top eight players compete in two round-robin groups of four, with the winners and runners-up advancing to the semi-finals.

Kvitova, ranked sixth in the world, and Osaka are in the Red Group in Shenzhen with top-ranked Australian Ashleigh Barty and Belinda Benic of Switzerland, who play each other in the second game on Sunday.

Defending champion Elina Svitolina is in the Purple Group alongside world number two Karolina Pliskova, Simona Halep and Bianca Andreescu.