The tragic incident occurred during the Badminton Asia Junior Championships in Yogyakarta, Indonesia ... as China's Zhijie faced Japan's Kazuma Kawano.

Footage of the incident, which we will not share, shows Zhijie collapsing, sending him crashing to the floor, where he appeared to convulse ... as his opponent and other officials stood watching.

Finally, help arrived after more than 35 seconds ... and Zhijie was loaded on a stretcher and taken to an ambulance. CPR was seemingly not administered on the court.

Sadly, Zhang passed away at a nearby hospital. The reported cause was cardiac arrest.

Many fans are upset over the response time from the medical team ... though an official, Persatuan Bulutangkis Seluruh Indonesia (PBSI), told BBC their tournament's medical teams had to "follow a rule where they needed the referee's permission before entering the court."

The Badminton World Federation said they're conducting a thorough examination surrounding Zhijie's death ... and want to see if the correct protocols were followed.

"Zhang's death at the Badminton Asia Junior Championships in Yogyakarta, Indonesia is a tragic occurrence, and we are taking all necessary steps to thoroughly review this matter in consultation with Badminton Asia and Badminton Association of Indonesia."

Fellow players at the tournament honored Zhang with a moment of silence ... and teammates raised his jersey at the podium.