About 150 Schalke supporters have clashed with riot police in the northern Greek city of Thessaloniki ahead of their team’s Europa League match against PAOK.
No arrests or injuries were reported from the violence hours before Thursday’s game.
Police said the group of German fans, who had previously visited a district full of beer parlors and restaurants, threw fireworks and stones at riot police escorting them.
Police responded with tear gas.
About 1,400 Schalke fans are expected to attend the game.