China's Li Shifeng suffered a first-round defeat at the All England Open Badminton Championships as the defending champion of the men's singles lost to Frenchman Toma Junior Popov in straight sets on Tuesday.

Li, 24, was crowned in Birmingham for the first time last March and took victory at the Asian Games in Hangzhou, beating teammate Shi Yuqi in both finals.

But the third seed made too many mistakes on Tuesday, outplayed by Popov 21-17 and 21-13. Li hasn't beat the 25-year-old in all three encounters.

Earlier, Popov's younger brother Christo Popov edged Lee Cheuk Yiu from Hong Kong, China 22-20, 17-21 and 21-16 to reach the last 16.

The men's singles top seed Viktor Axelsen breezily got past the opening round as the Olympic champion from Denmark saw off Indian Kidambi Srikanth 21-9, 21-9.

In the mixed doubles, China's defending champions Zheng Siwei and Huang Yaqiong were unchallenged as the pair won over American duo Vinson Chiu and Jennie Gai 21-6, 21-11 in 25 minutes.