Kawasaki Frontale were fined $15,000 and placed on one-year probation by the Asian Football Confederation on Thursday after their fans raised a controversial wartime Japanese flag during a recent Asian Champions League match in South Korea.
If the flag reappears during its probationary period, Kawasaki will automatically be forced to play one game in front of an empty stadium.
The AFC's disciplinary committee, which found Frontale guilty on charges of discrimination and spectator misconduct, notified Frontale through the Japan Football Association.