Zarina Diyas continued her stunning progress in the ECM Prague Open with a 6-4 6-2 win over Peta Kvitova to reach the quarter-finals.

Diyas, making her WTA Tour debut, was born in Kazakhstan but was given a chance because she is based in Prague. Ranked a lowly 295 in the world, she will next face Czech number one Iveta Benesova.

Benesova booked her own place in the last eight with a 7-5 6-4 win over gutsy Romanian Monica Niculescu.

Kateryna Bondarenko beat Germany's Kristina Barrois 7-5 7-5 to book a meeting with top seed Francesca Schiavone.