Czech police detained 150 Red Star Belgrade fans on Thursday after clashes before a Europa League playoff match against Slavia Prague.
Hundreds of the Serbian club's fans gathered in Prague's medieval Old Town Square with some hurling beer glasses and other objects at passersby and others smashing nearby windows.
Riot police, who had beefed up security ahead of the match following other crowd trouble involving Red Star fans, responded. Eight people were injured in the resulting clashes, although none seriously, news website IDNES reported.
"Police detained 150 fans. Of that number, 38 ended up at the police station for further investigation. Twelve will be charged with criminal offences," Prague police spokeswoman Andrea Zoulova said.
She said police were still determining what to do with the remaining 100 fans.
Slavia won the playoff round first-leg match 3-0.
In April, 95 fans were arrested following a derby between city rivals Partizan and Red Star after they clashed with police and set fire to 1,300 seats at Partizan's stadium.
Red star were forced to play one home match behind closed doors after the trouble.