Australian Open finalist Venus Williams fell at the first hurdle in the St Petersburg Ladies Trophy as Kristina Mladenovic cruised past her in straight sets at the Sibur Arena.

Williams, beaten by her younger sister Serena in Melbourne last week, entered the St Petersburg tournament at the second-round stage but had no answer to France’s Mladenovic, ranked 51 in the world, who stormed through 6-3 6-1.

The 23-year-old will face reigning champion Roberta Vinci in the last eight, with the Italian securing a 6-4 6-4 victory over Germany’s Andrea Petkovic.

Elena Vesnina ensured home representation in the quarter-finals, in which the Russian will face number two seed Dominika Cibulkova, after coming from a set down against Alize Cornet to prevail 2-6 6-3 6-3.

In the evening match, Slovakian Cibulkova beat Croatia’s Donna Vekic 6-2 6-2.

At the Taiwan Open, top two seeds Elina Svitolina and Samantha Stosur both advanced to the quarter-finals.

Ukraine’s Svitolina beat Lucie Hradecka 6-4 7-5 – while Australian Stosur recovered from losing the first set to beat Dalila Jakupovic 3-6 7-5 6-3.

Shuai Peng beat Katerina Siniakova 6-1 6-3 and Lin Zhu gave China two quarter-final hopes when she fought back impressively against Japan’s Kurumi Nara to win 4-6 6-1 6-2.