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.
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 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.
Football hooliganism has returned to the Europa League with a bang after a two-month break.
A brief fight broke out between Bristol City and Swansea City fans during their Championship clash at Ashton Gate on Saturday.
Millwall and Everton fans clashed in a mass brawl outside The Den ahead of their FA Cup tie on Saturday.
Nautico and Fortaleza fans clashed ahead of their Copa do Nordeste match on Tuesday night.