's-Hertogenbosch, The Netherlands (Sports Network) - U.S. Open champion Sam Stosur and French Open runner-up Sara Errani were among Monday's first-round upset victims at the $220,000 UNICEF Open, a final tune-up for Wimbledon.

Belgian qualifier Kirsten Flipkens upended the No. 1 seed Stosur in 7-6 (9-7), 6-3 fashion, while Ukrainian Kateryna Bondarenko bounced the second-seeded Errani, of Italy, 5-7, 6-3, 6-4 on the grass courts at Autotron Rosmalen. Bondarenko is rewarded with a second-round match Tuesday against former world No. 1 star Kim Clijsters, who captured this Dutch event in 2003 and was the runner-up in 2001.

A milder Monday upset came when former French Open champ Francesca Schiavone of Italy took out fifth-seeded Russian Maria Kirilenko 6-4, 3-6, 7-5.

In other action involving seeds, No. 3 Slovak Dominika Cibulkova drubbed Romanian Alexandra Cadantu 6-2, 6-2, No. 6 Italian Roberta Vinci handled Greek Eleni Daniilidou 6-3, 7-5, and No. 8 Russian Nadia Petrova downed Dutch wild cared Kiki Bertens 6-2, 6-4. Vinci is the reigning UNICEF champ, having beaten Aussie Jelena Dokic in last year's finale.

Additional Day-1 wins came for Dutchwoman Arantxa Rus, Polish qualifier Urszula Radwanska, Romanians Monica Niculescu and Irina-Camelia Begu, and Israeli Shahar Peer.

The 2012 UNICEF champion will collect $37,000.