TOKYO, Japan - Croatia's Jana Fett pulled off a shock as she knocked top seed Kristina Mladenovic out of the Japan Women's Open, beating her 6-4, 6-3.

The 20-year-old qualifier made a strong start to the match, and the Frenchwoman double-faulted to hand her opponent the first set.

Fett's forehand was firing in the second set, and she was quick to capitalise on her advantage against the reeling Mladenovic.

The World No.15 rallied briefly, looking impressive and pulling off a terrific lob as she won three games to get a foothold in the second set.

It was not enough, though, as Fett kept her nerve to serve it out and claim an admirable win.

Sara Sorribes Torro also staged her own shock as she beat fifth seed Samantha Stosur, 3-6, 7-5, 6-1.

Elsewhere, Kurumi Nara of Japan beat compatriot Naomi Osaka 6-3, 6-0, while Kazakhstan's Zarina Diyas beat Misaki Doi 3-6, 6-1, 6-1, and Kristyna Pliskova lost to another home favorite, Miyu Kato, 7-5, 6-3.

Aleksandra Krunic's fine form continued, beating the USA's Alison Riske in straight sets, 6-3, 6-4, and Christina McHale defeated Danka Kovinic 6-2, 6-4. There were also straight sets wins for Zhang Shuai of China, who beat Richel Hogenkamp 6-3, 6-3, and for Elise Mertens of Belgium, who beat Magda Linette 6-1, 7-5.