A hand grenade was found at a building used by ADO Den Haag fans on Tuesday morning.
Karlsruher hooligans clashed with their Waldhof Mannheim rivals in the southwest German city of Mannheim on Wednesday.
A Copa Argentina match between Newell's Old Boys and Villa Mitre was abandoned in extra-time on Sunday because of fan trouble.
Sunday's derby match between Panathinaikos and Olympiacos was abandoned after tear gas drifted into Athens' Olympic Stadium and affected players and fans.
A Polish IV Liga match between Karpaty Krosno and JKS Jaroslaw was abandoned on Sunday following a pitch invasion by home fans.
Bolton Wanderers fans clashed with cops at the DW Stadium during Saturday afternoon's Championship match against Wigan.
Panetolikos and PAOK fans clashed in the streets of Agrinio ahead of their Greek Super League match on Saturday.
Seven Newcastle United fans were arrested after a pitch invasion during Saturday's Premier League clash against Bournemouth at Dean Court.
A Polish lower-league match between Okocimski Brzesko and Tarnovia Tarnow was abandoned on Saturday after rival fans clashed on the pitch.
Aston Villa midfielder Jack Grealish was attacked by a Birmingham City fan during this afternoon's Championship match at St Andrew's.
Bayern Munich and Wolfsburg hooligans clashed in a mass brawl before yesterday's Bundesliga match.
Luzern fans staged a protest against the early kick-off time of their side's Swiss Cup quarter-final tie with Young Boys on Wednesday.