TOKYO -- Top seed Casper Ruud of Norway suffered a shock defeat to Spain's Jaume Munar in the first round of the ATP Japan Open here on Tuesday.

Ruud, ranked third in the world, lost to 58-ranked Munar 6-3, 6-3 in one hour and 35 minutes at the Ariake Colosseum.

The 23-year-old Norwegian, the beaten finalist at the French Open and US Open this year, also made an early exit in the South Korea Open last week, crashing out in the quarterfinals against Japan's Yoshihito Nishioka.

In other matches, South Korea's Kwon Soon Woo produced another upset by eliminating sixth seed Alex de Minaur of Australia 6-3, 6-2.

Fifth seed Nick Kyrgios of Australia breezed past Chun Hsin Tseng of Chinese Taipei, 6-3, 6-1. Britain's eighth seed Daniel Evans beat Moldova's Radu Albot 6-7(3), 6-1, 6-4 and ninth seed Borna Coric of Croatia defeated Thanasi Kokkinakis of Australia 6-4, 7-6(4).