England fans causing trouble while in Porto for the Nations League Finals have been dubbed "an embarrassment" by the Football Association (FA), which insists the perpetrators "are not welcome in football".
Gareth Southgate's team take on Netherlands in Guimaraes on Thursday for the right to face Portugal in the final of the inaugural edition of the UEFA competition.
However, England's involvement has already been marred by anti-social behavior from an element among the traveling fanbase, culminating in riot police charging supporters on Wednesday.
Another standoff between England fans and the Portuguese PSP force in the fanzone in central Porto. Police have shields out & bottles being thrown at them pic.twitter.com/a5V7n3wnXM— Sam Wallace (@SamWallaceTel) June 5, 2019
The incident occurred after bottles were thrown in a designated fan zone at Porto's Praca da Liberdade, where Portugal supporters gathered to watch their team's 3-1 semi-final win over Switzerland.
Although further large-scale violence was avoided, there were also clashes involving England fans and police around night spots on Rua da Fabrica and Rua de Candido dos Reis, which are adjacent to Praca da Liberdade in the city centre.
"The FA strongly condemns the scenes witnessed in Porto overnight," an FA spokesperson said.
"Anyone responsible for these disturbances cannot be seen as true England supporters and are not welcome in football.
"They are an embarrassment to the team and the thousands of well-behaved fans, who follow England in the right way. We are liaising with the UK Football Policing Unit."
There are fears of a repeat when a large contingent of England fans make the 55-kilometre journey to Guimaraes, following similar incidents during international away matches in Dortmund, Amsterdam and Seville over recent years.
Before the Nations League Finals, the FA launched a video campaign entitled 'Don't Be That Idiot', cautioning fans against anti-social behavior and it has expressed concerns over a "stag-do culture" on England trips to readily accessible western European venues.
Deputy chief constable Mark Roberts, football policing lead for the National Police Chiefs' Council, said: "The behavior we are witnessing is incredibly disappointing.
"A small number of the England fans out here continues to tarnish the reputation of the genuine fans who are simply trying to enjoy the football."