Groningen and Arminia Bielefeld hooligans clashed in the centre of Groningen on Saturday evening ahead of their friendly.
Pecsi MFC and Cibalia fans clashed on the pitch during a friendly match in Hungary on Saturday.
Cagliari and Pogon Szczecin hooligans clashed in the streets of the Sardinian capital after a friendly between the two sides on Friday.
A brawl erupted between Nantes and Brest fans following Friday’s pre-season friendly at the Mane Braz stadium in the north-western French town of Inzinzac-Lochrist.
Club America and Pumas fans clashed on the pitch during a friendly in Santa Ana, California, on Sunday afternoon (local time).
Sporting and Betis fans clashed near the Algarve stadium ahead of their friendly on Thursday.