China's defending champion Shi Yuqi suffered a shock exit in the first round of the BWF World Championships in New Delhi on Monday, losing a three-game battle against India's Ayush Shetty.

The World No. 1 fought back after dropping the opening game, but Shetty held off a late charge from the top seed to clinch a 21-14, 13-21, 21-19 victory in 73 minutes.

Shetty, making his debut at the World Championships, led 11-5 in the decider before Shi cut the deficit to one point in a tense finish. The 21-year-old home hope then closed out the contest to record his first victory in four meetings with the Chinese superstar.

The result represented a major turnaround from their previous encounter at the Badminton Asia Championships in April, when Shi swept aside Shetty 21-8, 21-10 in the men's singles final to capture his only individual title so far this season.

China's other men's singles players experienced contrasting fortunes, as Li Shifeng eased past Kazakhstan's Dmitriy Panarin 21-7, 21-10, while 16th seed Weng Hongyang was knocked out by Japan's Yushi Tanaka 21-17, 21-14.

In women's singles action, China's Wang Zhiyi got off to a comfortable start, needing just 36 minutes to defeat the USA's Beiwen Zhang 21-12, 21-13 and move into the second round. Fifth seed Han Yue recovered from one-game deficit to defeat Scotland's Kirsty Gilmour 20-22, 21-13, 21-13.

Also of note, the Republic of Korea's World No. 1 An Se-young opened her campaign with a 21-14, 21-13 victory over Bulgaria's Kaloyana Nalbantova.

China enjoyed a clean sweep in the day's doubles matches. In men's action, Huang Di and Liu Yang beat the USA's Zhiyi Chen and Presley Smith 21-14, 21-16, while Hu Keyuan and Lin Xiangyi cruised past Switzerland's Yann Orteu and Minh Quang Pham 21-6, 21-10.

On the women's side, Luo Yi and Wang Tingge defeated Denmark's Kathrine Vang and Mette Werge 21-11, 21-15 to reach the round of 32.