England football fans and police have clashed in Portugal ahead of Thursday's Nations League semi-final against the Netherlands.
Video on social media showed police, holding batons and riot shields, chasing supporters as Portugal's semi-final against Switzerland was screened in a fan zone in the centre of Porto.
An eyewitness claimed fans wearing England shirts and chanting England songs started throwing drinks and bottles when Portugal scored.
In the footage, several objects can be seen flying through the air in the direction of the police, who then charge towards the fans. Some of those watching cheered and filmed the altercation on their phones.
The behaviour of England fans has been condemned by the UK's National Police Chiefs' Council Football Policing Lead, Deputy Chief Constable Mark Roberts.
"Earlier this evening Portuguese police deployed riot officers against a group of England fans in the Main Square area of Porto," Roberts said in a statement. "It is believed the fans had been throwing bottles at Portugal fans who were watching the match in the same area.
"This is the second evening in a row where disorder has occurred in Porto. Last night there were issues outside a bar, where bottles were thrown and minor damage was caused. It is completely unacceptable.
"The behaviour we are witnessing is incredibly disappointing and again I would point fans towards the recent video from The FA - 'Don't be that idiot'. The behaviour of 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."
The FA "strongly condemned" the scenes in Porto on Wednesday night and described those involved as an "embarrassment" to England fans as a whole.
An FA spokesperson released on Thursday said: "The FA strongly condemns the scenes witnessed in Porto overnight. 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 liasing with the UK Football Policing Unit."
An unofficial Twitter account for English football fans has protested that Portuguese police have taken action for "no reason".
"The media only tell one side of the story. Portuguese Police pepper spraying people for no reason," EnglidsAway tweeted on Wednesday evening.
England are due to play the Netherlands on Thursday in their Nations League semi-final, 35 miles away from Porto in Guimaraes.