Trouble flared in Dortmund ahead of Germany's game in the city with Poland.
Violent scuffles broke out between German and Polish hooligans and riot police were showered with bottles in the city centre.
The trouble began when scores of riot police moved into the Alter Markt, a square where large numbers of German and Polish fans were drinking before the game. They were met by groups of German fans chanting and throwing bottles.
Police officers moved in to arrest individual known troublemakers who had been identified by spotters.
Then, as large numbers of fans moved towards the nearby Friedens-Platz, where there is a giant screen, there were small fights between Polish and German fans for about 10 minutes and they threw bottles at each other.
Several German fans, one draped in a national flag, were wrestled to the ground by police and placed in prison vans. Later, about 40 police special forces officers dressed in black body armour and balaclavas chased a group of hooligans through the main square, the Hansa-Platz.
The initial reason for riot police moving in to where fans were drinking appeared to have been to arrest known troublemakers as a preventative measure.
Dortmund police could not give any figures for arrests or injuries and said the situation was on-going.
Spokeswoman Inspector Saskia Schneider said: "At the moment there is a lot of action happening in the city centre. We have it under control but it is still happening."
She said it appeared German and Polish fans were not attacking each other but had instead attacked the police.