Slaven Bilic condemned the crowd troubles that arose at the London Stadium on Wednesday night.
West Ham United and Chelsea supporters clashed during the EFL Cup fourth-round encounter at the Stratford venue in what was an ugly night for English football.
I have noticed it, of course," Bilic said after the match.
"Whatever happened we are totally against it as a club and a team.
"For those kind of things to happen, especially in England, is unacceptable."
For the record, West Ham won 2-1 thanks to goals from Cheikhou Kouyate and Edimilson Fernandes, and will now meet Manchester United at Old Trafford in the quarter-finals.