Ajax fans clashed with cops outside the Johan Cruyff Arena ahead of their match against Juventus on Wednesday.
In a short statement posted on Facebook on Sunday, Cracovia hooligans wrote that they had broken off their relations with Ajax hooligans.
Clashes broke out inside the Athens Olympic Stadium ahead of AEK's Champions League match against Ajax on Tuesday.
Ajax fans were attacked by a mob of Benfica hooligans in the Portuguese capital after their Champion League match on Wednesday night.
A group of Ajax fans were attacked by Dynamo Kyiv hooligans as they relaxed at a Kyiv pub before a Champions League play-off tie on Tuesday.