Updated

Two-time champion and former world No. 1 Venus Williams was an easy first-round upset winner Monday at the U.S. Open.

The 33-year-old Venus leveled 12th-seeded surprise Wimbledon semifinalist Kirsten Flipkens, of Belgium, 6-1, 6-2 in 1 hour, 24 minutes at Arthur Ashe Stadium.

The currently 60th-ranked seven-time Grand Slam champion Venus captured the Open back-to-back in 2000 and 2001 and was the runner-up here in 1997 and 2002.

Meanwhile, third seed Agnieszka Radwanska and fifth-seeded Chinese star Li Na were also among the winners on Day 1.

The 2012 Wimbledon runner-up Radwanska, of Poland, routed Spaniard Silvia Soler-Espinosa 6-1, 6-2 at Ashe, while this year's Australian Open runner-up and the former French Open champion Li leveled Belarusian Olga Govortsova 6-2, 6-2 on the grounds at the USTA Billie Jean King National Tennis Center.

Also, 16th-seeded Wimbledon runner-up Sabine Lisicki, of Germany, handled Russian Vera Dushevina 6-2, 7-6 (7-3), 18th-seeded Spaniard Carla Suarez Navarro dismantled American Lauren Davis 6-0, 6-0, and 23rd-seeded American Jamie Hampton bested Spaniard Lara Arruabarrena 6-4, 6-2 for her first-ever U.S. Open match win.

Some other seeded winners on Monday were No. 25 Estonian Kaia Kanepi and No. 30 Brit Laura Robson, who handled Spaniard Lourdes Dominguez Lino, 7-5, 6-0. Kanepi overcame American Vania King, 4-6, 7-6 (7-4), 6-1.

A mild upset came when Austrian Patricia Mayr-Achleitner doused 29th-seeded Slovak Magdalena Rybarikova, 7-6 (7-2), 6-3.

Also advancing was American Coco Vandeweghe, who topped Serb Aleksandra Krunic 6-4, 7-6 (7-5).