TOKYO (AFP) - Denmark's Viktor Axelsen defeated badminton's world No. 1 Son Wan Ho in the men's singles semi-finals at the Japan Open on Saturday.

Axelsen, who beat two-time Olympic champion Lin Dan of China to clinch the world title in Glasgow last month, overpowered the South Korea with a 21-16, 21-16 win.

He now faces Malaysian Lee Chong Wei, who has won the Japan Open six times. The former world No. 1 booked a spot in the final after a 21-19, 21-8 win over China's Shi Yuqi.

In the women's singles, Spain's Carolina Marin, Olympic gold medallist last year, reached the final as Japan's Nozomi Okuhara dropped out owing to knee trouble.

Marin faces China's He Bingjiao, who beat countrywoman Chen Yufei 21-14, 25-23.

Okuhara, newly crowned women's world champion, was aiming to reclaim the trophy on home soil after winning it in 2015.

Home fans at the Tokyo Metropolitan Gymnasium expressed disappointment when the organisers announced her withdrawal.

"I did my best (to recover) but this morning, I wasn't in the condition to play," the 22-year-old told reporters, according to Sankei Sports.

"I was ready for a battle mentally but my body was telling me I couldn't," the tearful player said.