Hooligans in the Croatian capital Zagreb have stoned and set fire to a coach carrying fans of Greek football team PAOK, injuring three people.
The attackers, said to be fans of Dinamo Zagreb, the team playing PAOK in the Europa League on Wednesday, attacked the coach despite it having a Croatian police escort.
They smashed windows with stones and threw in burning flares.
Three of the 40 passengers, said to be VIP guests, needed hospital treatment.
Seven others were also hurt but refused medical help.
Eleven arrests were made and some of those detained were found to be on a register of hooligans, Zagreb police spokeswoman Jelena Bikic was quoted as saying by the Associated Press news agency.
The coach had been ferrying the Greek fans from the airport to their hotel.
The attack was carried out in such an organised way that the escort could not prevent it, Ms Bikic added.
Firefighters rapidly extinguished a fire in the coach.
Dinamo expressed regret about the incident and said they hoped that European football's governing body UEFA would not hold the club responsible as "the attack happened far away from the stadium".
Dinamo have been fined by UEFA several times in the past because of trouble from their fans at matches.
In a separate incident, a bus carrying Partizan Belgrade basketball players was stoned on Sunday night on the Croatian coast and one person was slightly injured, police said.