England football fans and police have clashed in Portugal ahead of a key semi final match.
Video on social media showed police holding batons and riot shields chasing supporters as a Portugal versus Switzerland game 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 fan zone was shut down following the incident.
It is also unclear as to what triggered the incident.
UK police have condemned as "completely unacceptable" clashes between England fans and Portuguese officers in Porto on Wednesday, as supporters watched Portugal play Switzerland in a fan zone.
Deputy Chief Constable Mark Roberts, National Police Chiefs' Council Football Policing Lead, said: "Earlier this evening Portuguese police deployed riot officers against a group of England fans in the Main Square area of Porto. 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."
England are due to play the Netherlands on Thursday in the Nations League semi final, 35 miles away from Porto in Guimaraes.
