In a statement FIFA said: "The FIFA disciplinary committee has opened disciplinary proceedings against the Swiss players Granit Xhaka and Xherdan Shaqiri for their goal celebration during the match Switzerland vs Serbia".
Granit Xhaka of Switzerland celebrates after scoring his team's first goal during the 2018 FIFA World Cup Russia group E match between Serbia and Switzerland at Kaliningrad Stadium on June 22, 2018, in Kaliningrad, Russia.
Arsenal midfielder Xhaka and Stoke City's Shaqiri trace their roots to Kosovo, a former province of Serbia where thousands were killed and tens of thousands more chased from their homes during a 1998-1999 conflict between Serbian forces and ethnic Albanian guerillas.
Xhaka's parents are originally from Kosovo, of Albanian heritage, and his father spent time in prison in Yugoslavia for his support of Kosovan independence.
However, a statement from Federation Internationale de Football Association on Monday confirmed that Xhaka and Shaqiri had been fined 10,000 Swiss francs (£7,632) each and Stephan Lichtsteiner 5,000 Swiss francs (£3,816), with all three also given warnings, having "infringed the Federation Internationale de Football Association disciplinary code for unsporting behaviour contrary to the principles of fair play".More news: Spain and Portugal through after incredible Group B climax
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Despite being recognised by UEFA, Serbia does not acknowledge Kosovo as an independent state, with relations between the Balkan nations remaining tense. Shaqiri had posted a photograph on Instagram of his playing boots, one with a Switzerland flag on the heel and the other with a Kosovo flag.
"It's just emotion", Shaqiri said regarding the gesture following Friday's win. I'm very happy to score this goal. "I think on and off the pitch we need to steer away from politics in football and we should focus on this as a sport that brings people together".
Football serves to promote friendship the world over, and the greatest football show on earth, the Fifa World Cup, should bring even greater friendship and understanding.
It is unclear what the investigation into Krstajic refers to, but in comments to Serbian reporters on Saturday, he said of match referee Felix Brych: "I wouldn't give him either a yellow or red card, I would send him to The Hague". Xhaka's brother Taulant plays for Albania's national side.
Xhara and Shaqiri could face suspension for celebrations that "provoke the general public".