Poland’s prime minister, Donald Tusk, has promised a “zero tolerance, ruthless” approach to hooliganism at tonight’s UEFA Conference League football final between Chelsea and Real Betis in the Polish city of Wrocław, following clashes between British and Spanish fans.

Yesterday evening, at around 7:30 p.m., groups of rival fans began throwing chairs and bottles at one another outside bars on one of Wrocław’s historic market squares.

“The English fans didn’t like the fact that the Spanish fans were sitting in an Irish pub, which means they sympathise with the Irish,” Tomasz Sikora, a spokesman for Wrocław city hall, told Polsat News. “That’s where the whole issue came from.”

“The police reacted immediately, which prevented further escalation of the conflict,” added Łukasz Dutkowiak, a spokesman for the local police. “The fans scattered in different directions and activities aimed at identifying them are still ongoing.”

Another clash then broke out around 11 p.m. involving around ten people. “A 31-year-old Spanish citizen, who was the most aggressive [among them], was detained,” while other participants ran away, said Dutkowiak, quoted by broadcaster TVN.

Separately, three other people from Spain were arrested for dismantling Conference League final flags. Sikora said that, in total, police made 515 interventions on Tuesday, the kind of level normally seen on New Year’s Eve.

Monika Kaleta, a spokeswoman for local police, told Eurosport that they are “expecting a possible escalation of clashes” today around the final, which begins at 9 p.m. local time in Wrocław’s 43,000-capacity Tarczyński Arena.

Around 2,000 police officers have been deployed to the city for the final, including many drafted in from other parts of Poland. Local newspaper Gazeta Wrocławska, however, notes that most of the thousands of fans who have come to Wrocław for the match are behaving peacefully.

In a statement issued on social media on Wednesday afternoon, Tusk “thanked the police for their decisive actions against the hooligans in Chelsea and Betis shirts in Wrocław”.

“Zero tolerance for violence on our streets!” he added. “We warn you: if necessary, the police will be even more ruthless today!”