Violent clashes in the build-up to Croatia and Republic of Ireland's Euro 2012 Group C clash in Poznan led to 14 supporters arrested in the latest of a series of incidents that have marred the opening days of the tournament.A couple of dozen supporters clashed in the city's main square on Friday night, though local police played down the severity of the incident, explaining that it was nothing exceptional.Renewed clashes on Saturday night, however, led to riot police being called to a fight in one of the city's pubs just after midnight, and 14 arrests were eventually made."It all broke out at one of the corners near Rynek and lasted for five minutes," local authorities told Goal.com."Police later identified a large group of fans and arrested 14 people. We believe that they are of three different nationalities and were waiting for most of them to sober up to further investigate the case."We are already analysing the CCTV footage. There is no need, though, for special measures to be taken for Sunday's match despite what happened before today's match."We haven't recorded any further disturbances, though we will continue to monitor the situation on the streets."The news comes just two days after Russia's impressive victory over Czech Republic was overshadowed by crowd trouble at Wroclaw's Stadion Miejski and news that - up until Friday - 16 reports of violent incidents had caused injuries to 314 people.