Yeah, it's one of the bigger rivalries, even in mondial football. It's not as bad as Rangers - Celtic (the religious aspect) or River - Boca and Fenerbahce - Galatasary (Argies and Turks, what can you say?) or Hajduk - Partizan (they went to proper war), but it's definitely a hot iron. They'll cave each other's heads in at any opportunity. People have died in the past.