Two stars of Switzerland’s World Cup team were fined by the tournament organizers on Monday for celebrating goals against Serbia last week with a gesture that honored their roots in Kosovo, the former Serbian province.

Granit Xhaka and Xherdan Shaqiri, whose ethnic Albanian families fled Serbian repression before Kosovo gained independence, were ordered to pay 10,000 Swiss francs each for crossing their hands into the sign of the double-headed eagle that adorns the Albanian flag after they scored against Serbia in a 2-1 victory on Friday in Kaliningrad, Russia.

Xhaka, whose father spent more than three years as a political prisoner in Kosovo before moving to Switzerland, made the gesture after scoring to level the match. Then Shaqiri, who was born in Kosovo and has the new nation’s flag stitched onto his right boot, slotted home a dramatic winning goal near the end of the match and wheeled away flashing the same sign.

The two players were fined for the “unsporting behavior” of, in the eyes of the officials, provoking Serbian fans in the stadium by making the gesture. The Football Association of Serbia was also fined 54,000 francs for “discriminatory banners and messages” displayed and chanted by Serb fans in the stadium.

Ultranationalist Serb hooligans reportedly chanted “Kill Albanians” during the game and were photographed wearing jerseys emblazoned with the face of Ratko Mladic, the Serbian general convicted last year of genocide and crimes against humanity for overseeing the ethnic cleansing of Muslims and Croats from half of Bosnia.

As the Bosnian-born journalist Nedad Memic pointed out, soccer hooligans from across the former Yugoslavia — who played a central role in igniting the bloody wars that ripped the former Yugoslavia apart along ethnic lines — seem to use the World Cup as an opportunity to express perverse pride over that legacy of violence.

After their loss to Switzerland’s immigrant-infused team, Serbia’s coach, Mladen Krstajic, even invoked the war as he called for the game’s German referee, Felix Brych, to be put on trial for failing to award a penalty after a clear foul on his team’s striker.

Serbia has refused to recognize Kosovo’s independence, which was won after NATO intervened militarily in 1999, launching airstrikes against Serb forces battling separatists in the province and bombing targets as far away as the Serbian capital, Belgrade. Russia has long supported Serbia’s claim to Kosovo, siding with their fellow Christian Orthodox Slavs against the territory’s Albanian Muslim majority.

Kovoso’s president, Hashim Thaci, a former leader of the separatist Kosovo Liberation Army during its war against Serbia, was among those cheering online as the goals went in.

Tensions between Albanians and Serbs have flared for decades across the Balkans, not only in Kosovo. In 2014, a soccer match between the national teams of Serbia and Albania in Belgrade had to be abandoned after rioting provoked by the sudden appearance of a small drone, flying low over the stadium and trailing an Albanian nationalist banner.

Video recorded in the stands that night showed Serbian fans breaking into the chant “Kill! Kill! Kill!” Albanians in response to the mechanized trolling.

When a Serb player eventually pulled down the banner — which declared that the Albanian people were the indigenous people of the Balkans, and featured a map of their nation expanded to include parts of Serbia — he was challenged by Albanian players. That game had to be called off after rioting Serbian fans, some wielding chairs, streamed onto the field and began attacking the Albanian team.