Denisa Allertova of the Czech Republic has defeated top seed Simona Halep in straight sets in the quarter-finals of the WTA Guangzhou International Women’s Open.

Unseeded Allertova pulled off the biggest upset of the tournament so far, beating the Romanian on Thursday, 6-4 6-3.

Halep, the world No.2, was beaten in the semi-finals of the US Open this month by eventual champion Flavia Pennetta of Italy.

In another upset, unseeded Yanina Wickmayer of Belgium defeated Romania’s Monica Niculescu, the No.6 seed, 6-2 6-2.

Sara Errani, seeded third, overwhelmed eighth-ranked Zheng Saisai, China’s top player, 6-1 6-0, leaving no more local singles players in the event.

And in the only battle of seeded players, Jelena Jankovic of Serbia (4) downed Svetlana Kuznetsova (5) of Russia 6-2 7-5.