Does it have something to do with past wars too?

There is some history between Serbs and Albanians and Serbs and Croats...

Some Latvians are also angry at Serbs because some of their fans bringed Russian flags into stadium during the first game (but, of course, nobody is talking about killing anyone here).

kristapsk

I remember reading this, fans of both teams shouted kill those Serbians

a shame sincerely