Police in Poznan have confirmed that they have arrested ten Polish fans, three Irish supporters and one from Croatia for fighting.
The incident is believed to have taken place in Poznan's main square last night ahead of the Republic of Ireland's Euro 2012 opener against Croatia this evening.
The fighting, which involved glass bottles and chairs being thrown, reportedly took place around 1am.
It is believed that some 30,000 Ireland supporters have descended upon Poznan ahead of their nation's first major since tournament since the 2002 World Cup.
