Croatia fans have a habit of disrupting and delaying matches at the European Championship.

On Friday, they added another ugly chapter to that history during Croatia's 2-2 draw with the Czech Republic.

Firecrackers exploded on the field in Saint-Etienne and burning flares rained on the turf, spewing smoke across the stadium — just as they did at all three Croatia matches at Euro 2012. The referee, Mark Clattenburg, stopped the game briefly.

Exactly why it happened, which provoked clashes among Croatia fans themselves, was not immediately clear. UEFA said it will hold open disciplinary procedures against Croatia following the incidents.

"Bravo Vatreni (Fiery) Croatia fans. And to you the Croatian team haters I have a message for you: you will pay for this!" Croatia's President Kolinda Grabar Kitarovic said on Facebook after the match.

Croatia fans have long been linked to far-right incidents. Groups from outside Zagreb have also opposed the widely unpopular Croatia soccer federation which is based in the capital city and led by Davor Suker, the former Real Madrid player who remains Croatia's top goal scorer of all time.

Suker's federation is responsible for all misconduct inside Euro 2016 stadiums by fans. Friday's incidents occurred in a section of a stand segregated for Croatia fans, to the side of one goal from where fireworks were thrown.

UEFA has already imposed a fine on the federation for previous incidents. Another one is likely after Friday's disturbances.

More punishments could be applied too, possibly for Euro 2020 qualifying.

UEFA already deducted a point from Croatia in Euro 2016 qualifying when fans created a swastika image on the field before a home qualifying match in Split. It was unclear if the swastika was due to fans expressing far-right views or a more calculated attempt to embarrass and shame the federation by forcing UEFA to act.

"As well as those who drew a swastika. Shame on you!" Kitarovic wrote Friday, recalling the June 2015 incident.

Croatia has had a core of right-wing supporters who identify with the World War II-era Ustasha regime.

In a notorious recent incident, veteran defender Josip Simunic was banned for 10 matches, including all of the 2014 World Cup, by FIFA after leading fans in chanting an Ustasha slogan after Croatia clinched its qualifying place.

Croatia is routinely forced to play in empty stadiums when hosting World Cup and European Championship qualifiers after far-right chants and songs are reported to FIFA and UEFA.

FIFA has already barred fans from attending the first two of Croatia's five 2018 World Cup home qualifiers in Zagreb in September and November. The federation will lose income and credibility.

"I think most of our supporters are true supporters," said Croatia midfielder Ivan Rakitic. "But just ten individuals can make problems."

The federation's reputation has suffered, even though Suker was elected last year by European soccer leaders to sit on UEFA's Executive Committee.

Under Suker, the federation has employed Simunic as a coach and maintained ties with Zdravko Mamic, the former president of Dinamo Zagreb who faces a range of graft and corruption charges.

Suker has declined recent interview requests from The Associated Press when on UEFA business, including at the Champions League final in Milan.