Violence erupted between football fans in Naples and San Sebastián.
In Naples, Eintracht Frankfurt fans defied a travel ban and clashed with Napoli fans, resulting in the set fire to vehicles and attacks on rivals with metal poles.
In San Sebastián, Real Sociedad and Roma fans clashed outside the Anoeta Stadium before the Europa League match, with chairs being hurled and flares being thrown.
In Naples, Italian police arrested five Napoli fans and three from Eintracht Frankfurt after over a hundred football fans went on the rampage in the city.
The clashes broke out on 27 November when German fans defied a travel ban and clashed with Napoli supporters ahead of a Champions League match between Eintracht Frankfurt and Napoli.
Reports suggest that the extremist "ultra" supporters fought running battles in the streets, and set fire to at least one police car.
The Italian authorities called it "guerrilla warfare" and six police officers were injured.
In San Sebastián, Real Sociedad and Roma fans clashed outside the Anoeta Stadium before the Europa League match.
Reports indicate that a bus of Roma fans was attacked before the two sides met tonight.
Photographs taken at the scene showed individuals picking up chairs and police using cordons to keep the two groups apart.
The game ended 0-0 and many fans remained in the area after the final whistle.
Although the two incidents had similarities, they had certain differences.
The clashes in Naples involved German and Italian supporters ahead of the Champions League match between Eintracht Frankfurt and Napoli.
It appears that they were prearranged and organised.
The violence in San Sebastián was more spontaneous, with clashes breaking out between rival supporters ahead of the Europa League match between Real Sociedad and Roma.