Fruhvirtova won 26 of 29 points on her first serve and converted four of 10 break chances in the 85-minute match.

Nao Hibino of Japan was a 6-2, 6-3 winner against sixth seed Qiang Wang of China.

The seventh seed Rebecca Marino of Canada defeated Poland's Katarzyna Kawa 7-5, 6-3 and fellow Canadian Eugenie Bouchard eliminated India's Karman Thandi 6-2, 7-6 (2).

Elsewhere, Ukraine's Lesia Tsurenko knocked out fifth seed Ekaterina Alexandrova of Russia 7-5, 7-6 (5) to advance to the quarter finals in Portoroz, Slovenia.

Tsurenko saved eight of 13 break points and will next face number three seed and 2022 Wimbledon champion Elena Rybakina of Kazakhstan, a 6-4, 6-1 winner against Tereza Martincova from the Czech Republic.

Second seed Beatriz Haddad Maia of Brazil moved on with a 6-1, 6-4 defeat of Spain's Cristina Bucsa.

The Czech Republic's Katerina Siniakova upended fourth seed Martina Trevisan 6-1, 6-4.

Romania's Ana Bogdan outlasted Slovenian favorite Tamara Zidansek 6-1, 6-7 (5), 6-1.

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