Reigning champion An Se-young suffered a "bitter" upset against Chen Yufei on Saturday as the Chinese player downed the top seed to set up a world championships final with Japan's Akane Yamaguchi in Paris.

The fourth seed stunningly bested the South Korean 21-15, 21-17 to book her spot in Sunday's title decider.

Yamaguchi had earlier seen off Indonesia's Putri Kusuma Wardani 21-17, 14-21, 21-6 in the other semifinal.