UEFA has said that football club Celtic have been fined 15,200 pounds ($19,000) after their fans waved Palestinian flags during their Champions League match against Atletico Madrid last month in Glasgow, Reuters reports.

The flags, which numbered in the hundreds, were deemed to be “provocative messages of an offensive nature”, UEFA has said in a statement.

Fans, who were warned by the Scottish club not to display flags before the October 25 game, could be heard singing “You’ll Never Walk Alone” while holding the Palestinian flags in a video shared widely on Instagram.

Supporters also unfurled two large banners at Celtic Park that read “Free Palestine” and “Victory to the Resistance”.