Riot police, using pepper spray and rubber batons, briefly moved into the stands to remove a Macedonian banner unfurled by the home supporters that had angered the visiting fans, with Greece in a long-standing name dispute with its northern neighbour.
"This deployment, however, was completely disproportionate. We cannot approve any of this, nor do we have any understanding for it," said Schalke board member Peter Peters in a statement.
Schalke said despite repeated efforts to have the fans remove it, the banner remained, further angering the Greek supporters.
"Fans in the north tribune had unfurled a banner of "Komiti Skopje", the ultras of (Macedonian club) Vardar Skopje who are friends of the Schalke ultras," the club said.
"According to police it was a case of agitation."
The incident in the second half lasted only a few minutes and was barely noticed by players and coaches of the two teams.
(Reporting by Karolos Grohmann, editing by Pritha Sarkar)
