Jana Fett sprung a surprise at the Japan Women's Open Tennis on Wednesday in knocking out top seed Kristina Mladenovic in the opening round.

Qualifier Fett, ranked 123rd in the world, prevailed 6-4 6-3 in Tokyo to book a meeting with Jana Cepelova in the last 16.

World number 15 Mladenovic, who reached the last four at the Australian Open and quarter-finals at Wimbledon this year, made a poor start and found herself 3-0 down in the opening set.

She recovered to get back on serve at 4-4 but a double fault at 4-5 15-40 gifted her opponent the lead.

And things unravelled swiftly in the second, Fett racing to 5-0 in front before a hold to love - sealed with Mladenovic's forehand wide - secured her progress.

Although Mladenovic's campaign was ended swiftly, there were no such problems for defending champion Christina McHale, who overcame Danka Kovinic 6-2 6-4.

Three-time winner Samantha Stosur followed Mladenovic in becoming an early casualty, as Sara Sorribes Tormo fought back from a set down to prevail 3-6 7-5 6-1 while Zarina Diyas, runner-up to Stosur in 2014, came from behind to defeat Misaki Doi 3-6 6-1 6-1.

There were first-round wins for Kurumi Nara, Shuai Zhang and Yulia Putintseva while Elise Mertens, Aleksandra Krunic and Miyu Kato all booked their places in the quarter-finals.