Polish president Karol Nawrocki has denounced a “scandalous” banner displayed by a group of Israeli football fans at a UEFA Conference League qualifying match on Thursday.

Supporters of Israeli club Maccabi Haifa held a large banner reading “murderers since 1939” close to the front of the stands and across a row of seats during the match against Raków Częstochowa in Debrecen, Hungary, an apparent reference to the Holocaust and the crimes committed by Nazi Germany.

On Friday, European soccer governing body UEFA announced that disciplinary proceedings have been instigated against Maccabi Haifa for “transmitting a message not fit for (a) sports event.”

Germany invaded Poland in 1939, with more than three million Polish Jews and 1.9 million non-Jewish citizens killed during the Holocaust. Poland was the center of Ashkenazi Jewry before the Holocaust, but by the end of World War II, just 10% of the community remained.

Considerable research by historians has found that some Polish individuals and groups did collaborate with the Nazi occupiers.

“Individual Poles often helped in the identification, denunciation, and hunting down of Jews in hiding, often profiting from the associated blackmail, and actively participated in the plunder of Jewish property,” according to the US Holocaust Memorial Museum.

However, recent Polish governments have sought to challenge that narrative of collaboration, and in 2018, passed a law making it illegal to accuse Poland of complicity in crimes committed by Nazi Germany, including the Holocaust.

“The scandalous banner displayed by fans of Maccabi Haifa insults the memory of Polish citizens, victims of World War Two, including 3 million Jews,” Nawrocki said in a post on X. “Stupidity that no words can justify.”

Meanwhile, Poland’s interior minister Marcin Kierwiński, said on X that “anti-Polonism and the outrageous distortion of Polish history by Israeli hooligans require strong condemnation. There is no, and will never be, agreement to such shameful practices.”

The Israeli Embassy in Warsaw also criticized the banner, photos of which have been widely shared on social media, describing it as “disgusting behavior.”