WEST HAM'S 2-1 win over Chelsea turned into turmoil when the London Stadium erupted into violence.
Chairs were ripped out and thrown and bottles and coins were used as missiles as both sets of fans squared up to each other inside the ground - Metropolitan Police later confirmed SEVEN were arrested and held overnight.
Riot police were called into the stadium after the violence broke out shortly before the final whistle.
Commander BJ Harrington, who was leading the police 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 welcome the condemnation from partners and have already started a post match investigation.
"We have already made seven arrests and will work tirelessly to identify people involved and bring them to justice."
Ian, a Chelsea supporter who was caught up in the violence, told BBC 5Live: "It was like being back in the 1970s.
"The amount of coins that were thrown, seats that were thrown, it was an absolute nightmare.
"I think there were people there who were on the lookout for trouble.
"If trouble was going to be there, they wanted to be at the front of it."
Fights among supporters and segregation issues had marred West Ham's earlier matches this season but improved stewarding by stadium operators London Stadium 185 had helped in recent weeks.
Chelsea had called on the Hammers and cops to "deliver a safe event" for when Antonio Conte's Blues travelled to their London rivals' ground.
But those pleas were not carried out as tempers flared and supporters clashed.
Furious fans can be seen being restrained by police in their attempts to get at their counterparts.
And one of the Chelsea faithful was struck in the head by a coin - drawing blood - apparently thrown by a rival supporter.
West Ham's statement read: "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."
But West Ham praised the majority of their fans, who they say "supported the team exceptionally and behaved impeccably."
He said: “I can say only I have noticed it of course, but the game was on and I was concentrating more on telling my defender Aaron Cresswell to watch the game, not what was happening off the pitch.
“I don’t know exactly what happened, but we are totally against it as a club and a team. For those kind of things to happen in England is totally unacceptable.”
Antonio Conte said: "I must be honest, I didn't see the situation because we were playing. I don't like these types of situation.
"It's important to see always the right atmosphere. In England we are used to seeing that. I'm sorry about this situation."
For all the ugly scenes off the pitch, Slaven Bilic's men were pleased to progress to the fifth round of the EFL Cup after beating Chelsea 2-1.
Gary Cahill's injury-time goal was not enough for Conte's side following Cheikhou Kouyate and Edimilson Fernandes goals.
West Ham now travel to Old Trafford to take on Manchester United on either November 29 or 30.