Five people were injured as Dutch fans attacked supporters before tonight’s semi-final in Dortmund, UK police said.
England fans in Dortmund before tonight’s game have warned to seek areas where there is a German police presence, a statement added.
The attacks happened at bars where England fans were drinking before the match, .
The statement from UK police said gangs of Netherlands fans identified as “risk supporters” had travelled to Dortmund ahead of the game and were known to the authorities.
“We are aware of some reports and videos circulating of disorder in Dortmund,” a statement from the UK Football Policing Unit (UKFPU) said.
“It appears that there have been several instances of Dutch fans attacking England fans in bars and attempting to steal flags.
“We understand this has resulted in minor injuries to five people. We are also aware that in addition to the tens of thousands of Dutch fans there to enjoy the game, there are groups of risk supporters who have travelled to Dortmund from the Netherlands.
“Our officers are at the location supporting German colleagues. We would advise supporters to be aware of their surroundings and seek areas where there is a German Police presence.”
Videos on social media showed supporters wearing orange Netherlands jerseys throwing stools and glasses outside a city bar, while England fans sheltered inside.
The Netherlands team said it had over 110,000 fans in Dortmund ahead of the match, while around 17,000 England supporters are estimated to be in the German city, meaning they are heavily outnumbered.
The majority of supporters congregated peacefully in the hours building up to the semi-final, although riot police were called to a fan zone after reports of overcrowding.