A group of partying West Ham fans were violently ambushed and attacked with flares, chains, bottles and batons by far-right Fiorentina ultras in the Czech Republic this afternoon, ahead of tonight's Europa Conference League final.
The celebratory mood soured in central Prague soon after 3pm when Hammers fans drinking in a bar were attacked by the Italians clad in black clothing and masks.
Several West Ham fans suffered cuts and bruises as the missiles flew. Police in the Czech capital said three West Ham fans and one police officer were injured in the incident while 16 people were detained.
One video showed the thuggish fans of the Florence club throwing chairs at the West Ham supports sitting under the arches outside the bar ahead of the Premier League Club's biggest European match in nearly half a century. Another clip showed the Ultras running down a Prague street carrying make-shift weapons.
As the police moved in to quell the violence, two stun grenades were launched into the Tekila Tekila bar in the city centre, causing loud bangs. Broken glass and a burnt-out chair littered the ground outside the bar after the attack.
Around 300 West Ham fans had been drinking happily, singing without causing any fear to police or locals when they were set upon by the Italian ultras.
As word went round the wider area that their fellow fans were being assaulted, Hammers fans moved towards the bar - and a group of riot police moved in to arrest the Fiorentina football fans causing chaos.
One West Ham fan who witnessed the scenes said: 'They targeted a group and attacked them quite violently then ran off before anyone could react. It was completely unprovoked. They were all ultras dressed in black. It was pretty grim.'
Another eyewitness, retired plumber John Brownlie from Cambridge, said: 'From nowhere about 100 men with chains, belts, bottles, and flares came round the street corner, and almost pushed over a lady and her baby in a pushchair.
'The woman quickly was quickly rushed inside to the bar, with her child, but two stun grenades were thrown in there, and caused some fire damage,' he added.
'This caused a lot of us to come out of the bar to find out what was going on, and then they started attacking us, punching and kicking us. When they ran, which would've been probably a minute later, we ran after them but the police blocked us.
'They were just cowards. West Ham fans didn't do anything wrong. This was an ambush,' Brownlie added.
Another West Ham fan, who did not want to be named, said 'a large group' of Italian fans attacked the bar.
'About eight Italians walked past, swinging bands and chains,' he said. 'Five minutes later there was a big group that come down the road and attacked us.'
The man said five West Ham fans were injured.
He said: 'Three of our mates (were injured), out of all of this lot there were five. Three of them were our mates. They've gone to hospital.' He said that one of his friends was 'quite badly' injured with a 'massive cut' on his head.
A 17-year-old witness to the attack on West Ham fans said that Fiorentina fans came around the corner 'trying to give it large'.
'We were all standing here, just having a glass,' he said. 'And they all come around the corner, trying to give it large. We done nothing wrong.'
He said that the Italian fans had 'chains and belt buckles'.
'They were throwing flares and firecrackers,' he said.
'They had chains and belt buckles and everything. They come here, try giving it, and then they ran down the road.'
Around 100 West Ham fans attempted to run towards the bar where their fellow fans were said to have been attacked but were kept at bay by around 50 police officers, some armed with automatic rifles and batons.
The ultras attempted to escape the police and ran through a busy paved shopping area. Some ran through the outside tables of a café where many people were dining, causing crockery, glasses and bottles to smash as tables were overturned.
Despite their efforts, they were rounded up and hemmed in outside a massage parlour. Women working within were seen peering through windows and taking pictures with their phones of the thugs.
MailOnline witnessed a group of suspected thugs being handcuffed and arrested before being led off through the crowds.
Police using tannoys, speaking in Italian, warned the remaining Florentina fans and ultras who were gathering to leave the area immediately.
In a statement on Twitter, along with a photograph of a number of Italian fans in handcuffs on the floor of a shoeshop, Prague's police forces confirmed that West Ham fans were attacked where in a bar by Fiorentina's fans.
'Italy fans attacked West Ham fans in a bar in Rytířská Street, injuring three. One policeman was also attacked,' the statement said.
'We have restricted the personal freedom of 16 people and we are currently investigating the whole incident. #policiepha'.
An investigation was ongoing and no more details were immediately provided.
It comes after similarly-cald hooligan supporters of AZ Alkmaar tried to get at West Ham players' families in chaotic scenes at the end of the semi-final in Holland.
Riot police have been on standby in the hours ahead of tonight's kick-off.
Earlier, one fan was detained by police for letting off an orange flair in the square, but later released after a ticking-off.
More than 10,000 West Ham fans were gathering in the fan zone to watch the match on a giant screen.
Supporters of their Italian rival without tickets were led to a separate fan zone.
After days of rain, the sun came out and lifted the spirits of the thousands of fans in Prague's Old Town Square as of pints were downed and bars were packed to the hilt.
Sam Nicola, 32, a London black cab driver who was wearing a claret and blue curly wig, said: 'I woke up this morning and my whole body went into this state of anxiety.
'I couldn't talk and I keep thinking about what might happen. It is far worse than normal butterflies, believe me.
'We just have to win, and I promised all my mates that I will wear this wig in my cab for a week if we do.'
His brother Jay, 35, who also wore a similar wig and drives a black cab, added: ' we have waited so long for this. But there was a lot of nerves.
'But I believe we can do it. We will bring that trophy home. We will win 2-1.'
London dentist Aditi Tanna, 28, who wore a West Ham hat and shirt said: 'It is so amazing being here with all these great West Ham fans. We have made many new friends.
'My boyfriend Ajay and I came into Prague on a train from Vienna this morning and for four more Euros we were put into first class and given a class of Prosecco so that was a great way to start the day.
'I feel it is getting better and better all the way to winning the cup tonight.
'We don't have tickets, but it is much more fun being here than watching it on TV from the sofa. '
Keilan Schemeri, 31, from Gibraltar whose father Joe is from London and a Hammer's fan said: 'It will be 3-1 to West Ham. We are going all the way.'
Former West Ham striker, Tony Cottee join supporters in the old town Square as a sign his name.
Actor and comedian James Corden, a lifelong West Ham fan, also flew into the Czech Republic and posed happily with supporters for photographs.
Folk hero Knollsy, who was dubbed the 'Angel of Alkmaar' after fighting off thugs out to attack West Ham fans last month, was mobbed by well-wishers as he walked through the square wearing a black West Ham shirt.
The final is West Ham's first in Europe since 1976, and they are bidding to win their first trophy since the FA Cup 43 years ago.
Greg Robson, 59, from Manor Park, east London, told the PA news agency he has been a season ticket holder for 43 years.
'First game was 1969, with my dad, sadly no longer with us,' he said. 'And I've had a season ticket since the age of 16. This is about my 43rd year now going home and away, following them abroad. I just love West Ham United.'
He said it felt 'unbelievable' to be in a European final.
'I was just one when we first won it, 11 in '76,' he said. 'So really, for me, this is the first time to actually go to one.' He said he booked his flight to Prague before West Ham had even made the knockout stages.
'We actually booked the flights when we were in the group stages,' he said. 'So it's a gamble that paid off.' He added that he will 'party all night' if the Hammers win.
'Just party, party all night,' he said. 'I've got an early flight in the morning, but I might be missing that.'
Andrew Hall, 54, from Surrey, said: 'If we're celebrating I could be here for another week.' He added that he had spent 'probably £1,000' on his trip to Prague, adding: 'But it's worth every penny.'
Steve Wick, 60, from Hertfordshire, said he had travelled for hours to make it to the Czech capital. 'We drove 13 hours,' he said. 'We got the shuttle over from Folkestone and then drove through. So 13 hours door to door.'
He said it had been 'years and years' since the team had had any major success.
'If we win this tonight it will be mega for the fans,' he added. 'It has been years and years since we've had any glory. And I think this is going to be it.'
Dan Lee from Romford said he had spent more than £1,000 on his trip to the final.
'All in, over £1,000, but it's what you do for West Ham,' he said.
He added that being in a European final meant 'everything' to him.
'Never did you think that little old West Ham would get this far,' he said.