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 really positive experience and keeping pretty much in what we have experienced with the majority of England fans over the last few years. 'People took to the spirit of the tournament and hopefully that will be the same here. 'I am not aware of any significant problems with England fans for at least a decade.' Portuguese police hemmed England fans into a small area to help contain them (there is no suggestion these fans - pictured on Tuesday night in the city centre - were doing so ) Told of Sportsmail's video of England fans chanting distasteful songs, he said: 'This is probably replicated in every resort in The Algarve and every resort in Spain. 'We are a few days away from a game that is taking place an hour's train ride from Porto. At what point does somebody stop being a tourist and start being a football fan? 'What I am saying is that there are issues day in-day out with anti-social behaviour among young people in particular right across the board in British society. 'It would be astonishing if that wasn't also reflected in football. 'We have always encouraged people to come to matches and enjoy the football and the great opportunity to make friendships out of the rivalry.' There were no arrests, but police are stepping up operations on Wednesday night Stephen Greensmith, 22, from Croydon, who is attending his first England match, said: 'It's fantastic that I could come and see our country play here with three of my friends. 'We are not here just for the football and are going to Lisbon to have a look around too. His friend Lahira Vaas added: 'It has cost each of us around £800 for the match on Thursday, the accommodation and the flights which isn't bad at all. 'We all watched Russia and saw what a great thing it was following England, so we decided we had to go to the next tournament.' Their fellow supporter Oliver Hock said: 'We are not interested in being with anybody who wants to cause trouble or sing offensive songs. We are just excited to see England play and see some nice places in Portugal.' As around 1,000 England fans sang, chanted and threw beer around, a senior British police source in Porto told Sportsmail: 'What we are seeing here is a new breed of lout. 'These are not established and known hooligans from years back. These are a type of hanger on. We don't recognise a single one. 'They have come here because flights are cheap as is the beer and they do it in the name of England. 'We haven't got the power to arrest here. If racist and bad language like that was used back home, then they could be lifted. 'All we can do is advise the local police if we spot anybody who shouldn't be here through being banned. 'There is a lot of beer being drunk and fans from three countries are here. So we are on alert. 'The police in Portugal are far more resilient and patient than we would be.' Porto police hemmed in the rowdy England fans on the waterfront. They took action when a football being kicked around to cheers bounced their way and confiscated it. But fan numbers were increasing with many bringing 12-packs of glass bottled beer to the area. Senior police Officers on Wednesday condemned the 'stag-do mentality' of some of the England fans Deputy Chief Constable Mark Roberts, National Police Chiefs' Council Football Policing Lead said: 'There are a significant number of fans in Portugal to watch the football. 'The majority of these have travelled simply to enjoy the football and the country itself, and they go largely unnoticed. 'It is the small percentage of fans who have a stag-do mentality, where too much alcohol is consumed and their behaviour becomes reckless and anti-social. 'While some of this behaviour may not result in arrest, it does not make it any more acceptable. 'We have a UK team working with local counterparts, however this remains a Portuguese policing operation and fans should expect police to take appropriate action where necessary to prevent the risks posed by troublemakers. 'We fully support the recent initiative from The FA and I would encourage fans to watch the video entitled 'Don't be that idiot…' and reflect on their own behaviour from the past 24 hours. 'We want supporters in Portugal to celebrate and enjoy the atmosphere and football - not have their experience marred by the mindless few.' All rights reserved for this news site dailymail and under his responsibility