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.
Republic of Ireland supporters are out in force in Poznan today to support their country ahead of tonight's match against Croatia in Euro 2012.
For full coverage of the Republic of Ireland's opening match in Euro 2012 visit ITV Sport.
Here's a selection of images of supporters enjoying the sunshine in Poland.
President Michael D Higgins and his wife Sabina meet football fans from Andersonstown in West Belfast. Credit: Niall Carson/PA Wire/Press Association ImagesRepublic of Ireland fans pose for pictures in the main square in Poznan ahead of tonight's match against Croatia. Credit: Niall Carson/PA Wire/Press Association ImagesSupporters pack the main square. Credit: Niall Carson/PA Wire/Press Association ImagesSupporters gather before kick off. Credit: Niall Carson/PA Wire/Press Association Images
Giovanni Trapattoni has been in football management since 1972. Credit: Niall Carson/PA Wire/Press Association Images
Republic of Ireland manager Giovanni Trapattoni is "grateful to the Irish people" for believing in his project as his team attempt to kick off their Euro 2012 campaign with victory over Croatia.
The 73-year-old Italian, who has been in charge of the national side since 2008, paid tribute to supporters - many of whom will be turning out in their droves in Pozna tonight.
"I am really, really grateful to the Irish people because they believe in our project."
He continued: "For me and for [assistant manager] Marco Tardelli, we have given Irish people what Ireland has asked for.
"This has been the same through all my career. I have the same determination and the same concentration and the same attention to detail."
For full coverage of the Republic of Ireland's opening match in Euro 2012 visit ITV Sport.
Father and son Joe and Ronan Organ, from Cork, travelled to Euro 2012 in a campervan from Berlin. Credit: Niall Carson/PA Wire/Press Association Images
Father and son Joe and Ronan Organ from Cork are just two of thousands of Republic of Ireland fans who will be supporting their country against Croatia at the Miejski Stadium in Poznan today.
For full coverage of the Republic of Ireland's opening match in Euro 2012 visit ITV Sport.
