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, UEFA said on Wednesday.

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

Fans, who had been warned by the Scottish club not to display flags before the Oct. 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".

Gaza's Hamas-run government says at least 13,300 Palestinians have been killed, including at least 5,600 children, in the war with Israel.

Celtic are fourth in Champions League Group E on one point after four games.

They were also fined 10,000 pounds for fans blocking passageways and using pyrotechnics.