The president of a French soccer team accused Ukrainian fans of acting like "rabid dogs" after a match between Ukraine's Dynamo Kyiv and French club En Avant de Guingamp (EAG) descended into chaos Thursday.

The referee was forced to stop the Europa League game 15 minutes early when a small group of masked Ukrainian fans invaded the pitch and attacked the supporters of the rival team.

The Ukrainian team was winning 2-0 when a group of so-called "ultra" Kyiv supporters fought past the security staff separating fans from the stadium's running track and marched onto the 20 or so French Guingamp fans that were seated in the sidelines.

As the French fans were evacuated from the stadium, the Ukrainian supporters continued the fight among themselves, throwing chairs at the security staff who got in their way.

Minutes after the incident, Guingamp President Bernard Desplat told French radio station RMC that the Kyiv fans weren't supporters but "militiamen."

Dynamo Kyiv's Vice President Oleksiy Semenenko responded by accusing French supporters of willingly provoking their Ukrainian counterparts by brandishing "the flag of one of the fake states in eastern Ukraine."

Meanwhile, some Twitter users claimed that Guingamp fans had hung the blue, white, and red French flag upside down, causing it to resemble the Russian flag.

Speaking to VICE News on Friday, Guingamp spokesman Christophe Gautier denied any provocation by the French, saying that supporters "didn't have any French or Russian flags — just the flag of Brittany, and the club banner."

Gautier added that he believes the Ukraine team could be using the excuse of provocation to avoid the heavy fines handed down by the Union of European Football Associations (UEFA) — the administrative body that represents Europe's soccer teams — for pitch invasion.

Gautier is convinced the attack was premeditated. "Our security director received a text message a few minutes before the incident occurred," he told VICE News, "which hopefully gave our supporters enough time to swiftly evacuate the stadium, and return to their hotels in small groups."

Yet not everyone is quick to believe that the brawl was an elaborate pre-planned scheme. "Those who attacked the French look very young," Ronan Evain, a PhD candidate researching football fandom in former Soviet Union countries, told VICE News. "They were most likely a bunch of hot heads, trying to show off. I get that the Guingamp supporters were afraid, but it really wasn't that big a deal. No one was really going after them — they were probably just going after their banners."

This is not the first time that hardcore Ukrainian soccer fans have violently clashed with opponents. In December of last year, several supporters of France's Saint-Etienne team were hospitalized in Kiev following a violent brawl with fans of the Dnipro Dnipropetrovsk soccer club, during another Europa League match.

Gautier had advised Guingamp fans not to follow their team to the Ukraine for such security reasons. In 2012, several other European teams warned their supporters not to travel to the Ukraine for the UEFA championship, also to avoid clashes with local fans.

Ukranian "ultras" have a thuggish reputation throughout Europe and are known for their anti-Semitism, racism, homophobia and penchant for neo-Nazi symbolism. There are between 15,000 and 30,000 ultras in Ukraine, according to Esquire.

But despite their reputation for oafish brutality, Kyiv's ultra supporters have undergone an image change in the past year, putting aside their passion for brawling to defend Ukraine's Euromaidan protesters against the police and pro-government vigilantes. Many ultras were dragged into Ukraine's political crisis that erupted in 2013 and joined the thousands of others that poured into Kiev's Maidan Square to protest the government of former President Viktor Yanukovych.

"If you don't get interested in politics," one ultra told Esquire, "then politics will get interested in you."

Despite the lack of a common political agenda, many of the ultras chose to side with the protesters, against the former President Yanukovych, in calling for Ukraine's integration into the European Union. One of the reasons for this, said Bennets, is that ultras had followed their teams across Europe and had come to regard EU integration as a positive thing.

"The ultras mobilized in the early days of the conflict," Evain said. "Their ability to fight and the hierarchy within their group allowed them to secure and organize the protests."

Evain also pointed out the pan-national solidarity that developed between Russian and Ukrainian ultras. "Some Russian ultras supported the pro-Kiev Ukrainian ultras during the Maidan protests, in the name of pan-Slavism, and in defiance of the Russian authorities," Evain said.

According to Esquire, some 100 ultras fought in the eastern city of Donetsk during fighting there last June, in units such as the Azov Battalion — one of several volunteer paramilitary units fighting pro-Russia separatists. For Evain, this type of mobilization is more of a personal initiative than a movement, and "there is no common ultra front in eastern Ukraine."

Evain told VICE News the Ukrainian ultras have recently been organizing friendly soccer tournaments and marches for national unity — initiatives would have been "unthinkable a few months back." This newfound solidarity could explain why a large group of ultras rushed in to stop the fighting during Thursday's game.

Thursday's match was eventually restarted 15 minutes after the end of the brawl, ending with a 3-1 victory for Ukraine's Kyiv team.