Croatian fans threw chairs, bottles and flares at Polish riot police in the city of Poznan as they clashed ahead of Sunday's Euro 2012 game between Croatia and Ireland.
Three people were arrested after the incident in Poznan's old town square, where thousands of Irish and Croatian fans, many clad in the national red-and-white checkerboard shirts, gathered ahead of the match.
The police said it would examine closed circuit video from the centre square to identify additional culprits. Croatia beat Ireland 3-1 in the Group C match.
More top news
World record setting climber Ueli Steck - known for his speed at scaling mountainous terrain - has died in an accident near Mount Everest.
John McDonnell says voters can expect to see "no increases in income tax for middle or low earners" in Labour's election manifesto.
The prime minister has confirmed the Conservative government will not increase VAT if they win the General Election on June 8.