It all went down at Trabzonspor's home 3-2 defeat at the hands of Fenerbahce ... when the losing team's supporters got so upset over the Super Lig result, they started attacking the opposing players.

But Fenerbahce ended up getting two victories on the day ... 'cause players like Bright Osayi-Samuel and Michy Batshuayi put a beating on intruders -- and it was captured on video.

Batshuayi used his feet for more than footy -- kicking a fan who was approaching him.

Osayi-Samuel was also shown throwing a punch at two fans at once.

Security tried like hell to break up the brawl ... but not before even more spectators made their way to the pitch.

FIFA President Gianni Infantino released a statement on the ugly scene ... saying, "The violence witnessed after the Turkish Super Lig match between Trabzonspor and Fenerbahce is absolutely unacceptable -- on or off the field, it has no place in our sport or society."

"All players have to be safe and secure to play the game which brings such joy to so many people all over the world."

He added ... "I call on the relevant authorities to ensure that this is respected at all levels and for the perpetrators of the shocking events in Trabzon to be held accountable for their actions."