Riot police were forced to intervene following West Ham's win over Anderlecht at London Stadium after sections of the home crowd were pelted with flares and seats by travelling fans.
Earlier in the evening, one fan was wrestled away by stewards after running onto the pitch during the fixture, ahead of the post-match disruption.
Anderlecht boss Felice Mazzu claimed to have not seen the flares, but a club spokesperson said after the match: "We don't tolerate this kind of behaviour from our fans and we apologise to West Ham."
