Fourteen soccer fans were detained in the western Polish city of Poznan on Saturday night after police broke up a fight in the main square on the eve of the Euro 2012 Group C game between Ireland and Croatia.
Poznan police spokesman Andrzej Borowiak told Reuters officers had moved in swiftly after fighting broke out and some fans began throwing bottles and beer garden furniture in the square.
Most of those involved were chased away, with police arresting 10 Poles, three Irish fans and one Croatian, he said.
"We are still checking on the TV monitoring footage if these fans were really involved," Borowiak added.
"Currently they are being held for questioning."