Defending champion Alison Van Uytvanck secured a narrow win against Vera Zvonareva in the Hungarian Ladies Open Wednesday.
The top-seeded Belgian booked her place in the round of 16 with a 7-5, 7-5 victory in a match which lasted one hour and 55 minutes.
No. 3 seed Pauline Parmentier also advanced to the next round with a comfortable straight sets win against Czech Tereza Smitkova.
Russian Anastasia Potapova became the first player to secure a place in the quarterfinals after she stunned No. 6 seed Andrea Petkovic 6-2, 7-5.
"I was really waiting for this match because it was quite special," said Potapova after the match. "When I was 10 years old I was watching [Petkovic] play the quarterfinals in all the big tournaments -- she was an idol of my grandmother!"
Potapova, 17, will meet Sorana Cirstea for a place in the last four after Cirstea shocked No. 4 seed Aleksandra Krunic with a straight sets win.
No. 5 seed Ekaterina Alexandrova saw off Greta Arn while No. 8 seed Marketa Vondrousova defeated Spaniard Georgina Garcia Perez to advance into the round of 16.
Amercian Madison Brengle cruised into the next round with a straight sets victory over Fanny Stollar and Irina-Camelia Begu recovered from a set down to beat Mona Barthel 4-6, 6-1, 6-4.