Police in Portugal are braced for crowd trouble as up to 20,000 rowdy England fans descend on Porto ahead of Thursday night's match against Holland.
Hordes of boisterous supporters taking advantage of budget airfares and cheap booze have spent two nights in Porto singing anti-German and anti-IRA songs, forcing some bars to close down.
But thousands of tickets have been sold online by UEFA to un-monitored England fans and one police officer here said: 'This could be like 500 or more stag parties coming together at the same time.'
Some England fans have been filmed chanting some distasteful songs this week
England fans pictured in the city centre of Porto on Wednesday ahead of Thursday's game
Supporters enjoy a beer in the sun as they hope England go on to win the Nations League
Thousands of supporters have descended upon Portugal in anticipation for the Nations League
A major security clampdown is underway with teams of armed police on standby as fans from England, Portugal, Holland and Switzerland gather in the city.
One officer patrolling the crowds of boisterous fans on Wednesday night said: 'This could be like 500 stag parties coming together at the same time.'
Officers in charge of policing fear a number of hooligans have arrived in Portugal who stayed away from the World Cup in Russia after thousands of tickets have been sold online by UEFA to un-monitored England fans.
Sportsmail witnessed two nights of rowdy and drunken behaviour on the waterside of Porto as thousands of fans converged on the city for Wednesday evening's first match.
Beer can be bought for as little as £2 and glasses of port for around the same price and fans honed in on supermarkets to stock up.
Around 500 gathered outside Ryan's Irish bar in Porto early on Wednesday forcing the owner to close his business down after groups sang loud football chants outside his bar for the second consecutive night.
Some England fans have produced rowdy behaviour ahead of their Nations League semi-final (there is no suggestion these supporters were doing that)
Hordes of boisterous supporters have taken advantage of budget airfares and cheap booze (there is no suggestion these supporters were doing that)
They have spent two nights in Porto singing anti-German and anti-IRA songs, forcing some bars to close down (there is no suggestion these supporters were doing that)
Up to 20,000 England fans are expected in Portugal for their clash with Holland on Thursday
England fans pictured drinking and chatting in the city centre of Porto on Tuesday
Some urinated in side streets and police called in teams of street cleaners to clear piles of bottle and broken glass once the rain came down and forced the supporters to disperse.
They sang 'Ten German bombers', 'No surrender to the IRA' and 'Tommy Robinson - he's one of our own' as Portuguese police hemmed them into a small area to help contain them.
There were no arrests, but police are stepping up operations on Wednesday night when Switzerland play Portugal and Dutch fans start to flood in for Thursday's match with England at the 26,000-seater Estadio D. Alfonso Henriques in Guimaraes.
England fans have snapped up around 18,000 tickets, despite their official allocation was 10,000.
Banned from travelling are 127 Three Lions followers who received suspensions from the Football Association and had to surrender their passports five days before kick-off.
Beer can be bought for as little as £2 and glasses of port for around the same price in the city
Some supporters urinated in the side streets (there is no suggestion these fans were doing so)
The FA, aware of the many thousands travelling to support England for the first time, issued a video warning urging fans to behave.
Manager Gareth Southgate appeared on the film which pleaded: 'Don't Be That Idiot'.
Kevin Miles, Chief Executive of Football Supporters' Federation, told Sportsmail: 'Russia was a