Wednesday night's clash between West Ham and Chelsea proved to be tense off the field as well as on. Scotland Yard said seven men were arrested for public order offences following the game at the London Stadium, in Stratford, east London.
A further 30 people were issued with directions to disperse under antisocial behaviour legislation ahead of the EFL Cup match, the Metropolitan Police said.
The force said it deployed a "significant number" of officers in the stadium to deal with the "unacceptable" scenes at the derby match.
Commander BJ Harrington, who led the operation, said: "Although the vast majority of people left the stadium peacefully and were well behaved, there were a minority of people who attended the match that were clearly intent on being involved in confrontation and violence.
"Despite extensive work with both clubs and the London Stadium partners as well as a large and robust policing operation, there were unacceptable incidents inside and outside the stadium, before, during and after the game.
"We have already made seven arrests and will work tirelessly to identify people involved and bring them to justice."
Missiles including coins and seats were launched between rival fans. Stewards struggled to maintain segregation behind the Hammers' goal towards the end of the match, which West Ham won 2-1.
Both clubs issued statements condemning the skirmishes, the circumstances of which are under investigation by police.
A Chelsea spokesman also said: "The club is extremely disappointed to see disturbances at the end of tonight's game and we condemn such behaviour."
West Ham manager Slaven Bilic described the scenes as "unacceptable", while the club "unreservedly" condemned those involved, who they will seek to identify.
The club said: "Once identified, those found to have acted improperly will be banned from attending any West Ham United fixtures for life and we will request the courts serve banning orders to prevent these individuals attending any other football."