Fighting has broken out between football fans ahead of the Arsenal versus FC Köln match.
Video footage published on social media shows a fight in the Soho district of central London.
A group of about 10 fans are shown throwing punches and trying to kick each other while hundreds of other fans march along Wardour Street singing.
Jesper Lofgren posted on Twitter: "#FCKOLN on Wardour street just now #EuropaLeague"
It is was unclear what the fight was about.