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Fans' behaviour unacceptable - Bilic

Crowd trouble marred West Ham's EFL Cup fourth-round home win over Chelsea, with police making seven arrests.

Plastic bottles, seats and coins were thrown during the Hammers' 2-1 victory at London Stadium as hundreds of supporters clashed and riot police entered the concourse.

It is the latest outbreak of disorder at West Ham's new ground this season.

West Ham boss Slaven Bilic called the behaviour "unacceptable", adding: "We are totally against it as a club."

The Premier League club says it will ban any fans involved for life and is confident it can identify those responsible via its high-definition CCTV system and through fans' ticket purchasing history.

The Football Association and EFL are also investigating. A league spokesman called the incidents "distasteful and unwelcome".

Security was boosted for the London derby and an alcohol ban imposed as part of a "robust policing plan" following crowd trouble at the stadium this season.

Stewards and riot police intervened when fans came together in the stadium

Until Wednesday's match, the Metropolitan Police have not deployed officers inside the stadium because the radio system emergency services use to communicate will not be operational until 2017.

This season, the Hammers' first at the former Olympic Stadium following their move from Upton Park, 23 fans have been banned from the ground.

Four people were arrested following disorder at the Premier League match against Middlesbrough on 1 October, while there were clashes in the stands during the defeat by Watford in September.

The Metropolitan Police, who made seven arrests for alleged public order offences, described Wednesday's incidents as "unacceptable" and said 30 people were prevented from attending the match.

'Someone will get killed there'

West Ham v Chelsea: Eight-year-old caught up in football violence

Bilic added: "For those kind of things to happen, especially in England, is unacceptable."

Chelsea manager Antonio Conte said: "I don't really like to see these situations."

One fan at the game told BBC Radio 5 live it "was an absolute nightmare", adding: "If they don't close that stadium someone will get killed there."

West Ham said in a statement they "unreservedly condemn" fans' behaviour and will work to identify those supporters involved, while Chelsea said they were "extremely disappointed to see disturbances".

Police commander BJ Harrington said: "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 a large and robust policing operation, there were unacceptable incidents inside and outside the stadium, before, during and after the game."

Chelsea season ticket holders Paul Streeter and his eight-year-old daughter, Victoria, were sitting in the disabled section and got caught up in the violence.

"My daughter was hit with seven coins all over her body", said Mr Streeter. "We were watching the game in the front row near to the home fans - suddenly there's a whole load of coins coming over. Other kids were hit, it was not just my daughter.

"Victoria has been going to football since she was two, she's never experienced violence like this before or the aggression we have had to suffer. We want to take this matter further. It is disgusting.

"Stewards and police were not reacting. They should have dragged the crowd back and dealt with them."

'An agenda against West Ham'

West Ham fan and blogger Sean Whetstone told BBC Radio 5 live that coins were thrown by some Chelsea fans and some West Ham fans then retaliated.

He said: "Football has trouble, but it is not reported elsewhere. There is trouble at Stamford Bridge every season when West Ham play Chelsea. It feels like there is an agenda against West Ham.

"There is a limited amount of police inside the stadium. It is the stewards' job to sort that out inside the stadium. They have learned a lot already but there is much to do.

"It is a new stadium, an iconic stadium and I believe that a small amount of away fans come to prove a point. Are some West ham fans unhappy? Do they feel unsafe? Yes they do.

"West Ham are doing enough. They have the best CCTV available and they will look at all of the footage and anyone who threw anything will be banned for life. There is zero tolerance."

'Atmosphere turned toxic'

BBC's Richard Conway at London Stadium:

With West Ham cruising towards the quarter-finals of the EFL Cup their fans were taking great delight in taunting Chelsea's 5,000-strong support.

Then tension and vitriolic chanting turned into violence. Fans told me after the game how they and their children were pelted with coins.

The atmosphere turned toxic, with attention now focused not on the pitch but on events in the stand.

A Chelsea fan broke through a line of stewards into the area dividing supporters, balancing on the tops of seats covered in claret tarpaulin. He goaded his rivals before retreating.

Then the two sets of fans surged towards one another on the stadium concourse, which sits at the top of the lower section of the ground. It took a number of stewards, eventually backed up by riot police, to quell the standoff.

The final whistle came soon after and fans eventually left the stadium. But the damage by then had been done.

I started watching football as a kid in the mid-1980s, when fan violence was rife within the game. The end of this match made it feel like I had momentarily stepped back in time.

A fan gets past a cordon of stewards to approach West Ham fans

'Sad scenes'

BBC Radio 5 live presenter Jonathan Overend, commentating on the game, said: "This has been brewing all night.

"It's been hard to watch the match because of the flash points developing. The stewards have got a tough job here. Fans are trying to burst at each other.

"They've been hurling missiles at each other. It looks like plastic bottles and I've seen what looks like three or four plastic seats being thrown."