I'm guessing the first event in Nice is an isolated incident that can happen at any venue - apparently a bottle thrown by a local youth and that 'sparked' the prob with this gang of local youths in Nice. I'm not reading about ensuing violence through the night and will be very surprised if this scenario arises. The other incident was again an isolated one but, as hibeejim says, there is some previous bad blood between factions of extreme RW Polish fans and elements of NI 'prody inspired' fans who I hope are in a minority within the mix of NI fans who wanna see their team doing well for a change.