Police will beef up their presence at the Western Sydney Wanderers' upcoming A-League matches after fans were filmed harassing diners before last weekend's Sydney derby.
Video emerged on Tuesday of a group of Wanderers supporters outside a Parramatta restaurant, yelling, swearing, spitting and hurling a glass at a Sydney FC fan who was eating with friends.
Children and elderly people were among those caught up in the violence at a steak restaurant near the Riverside Theatre.
There was also violence inside Parramatta Stadium, with a number of people invading the pitch.
Wanderers executive chairman Lyall Gorman condemned the behaviour and said his club accepted responsibility.
"Our club's got to take full ownership for this, and we do," executive chairman Lyall Gorman told ABC radio on Tuesday.
"We don't stand for this and nor will we stand for it.
"It's not a part of our brand in any shape or form and we'll do whatever we can with stakeholders to weed it out of the game."
Seven people have so far been arrested over what NSW Police Commissioner Andrew Scipione described as "abhorrent" behaviour.
"We think estimates are about 30 to 50 hoodlums - and that's what they were - decided to go out there and carry on and potentially spoil it for 20,000 fans and those people that paid their ticket - they deserved to have a great day out," he told reporters on Tuesday.
"But on this occasion, we saw this behaviour and it was abhorrent. We won't let that happen again."
Commissioner Scipione said while police were reviewing CCTV footage of the incident, they were also preparing for future matches and would increase the number of police deployed.
"My thoughts and my mind turn to where we are at in preparing for the future," he said.
"Let me assure you we will have more than sufficient resources out to deal with any problem or trouble makers that might have a plan to go out and spoil someone's day."
Gorman said 14 supporters have already been banned from the game for at least five years during the club's inaugural A-League season, and predicts more to come.
"We've still got this minority hooligan thug element who will try and break those rules wherever they can," he said.
"Be assured: they will be banned for a very, very lengthy period from our game, let alone what actions follow through from normal legal due process."
The Wanderers play their final regular match against Newcastle Jets at Hunter Stadium on Friday and are guaranteed a home semi-final.