Tuesday's Champions League qualifier between AEK Athens and Dinamo Zagreb has been postponed after a fan was stabbed to death in the Greek capital.
The Greek supporter, 29, died following brawls between rival fans outside AEK's Agia Sophia Stadium in a northern suburb of Athens on Monday evening.
Police said eight others were injured and 98 arrests were made.
Uefa had banned visiting supporters from both legs of the third-round qualifying tie over security concerns.
European football's governing body said following the trouble and in consultation with the local authorities, the match had to be postponed.
"Uefa deplores in the strongest possible terms the appalling incidents that took place in Athens last night and resulted in the loss of a life," Uefa said.
"While expressing our deepest sympathy to the family of the victim, to AEK Athens FC and its fans, we would like to reiterate that violence has no place in our sport and we expect that those responsible for this terrible act be arrested and consigned to justice in the shortest delay."
The return leg in Croatia will go ahead as planned next Tuesday,15 August with the game in Athens to be rearranged for either Friday, 18 August or Saturday, 19 August.Greek police said the trouble started 90 minutes after Croatian side Dinamo had completed a pre-match training session at the stadium in Nea Philadelphia and left under police escort.
Between 100-120 Dinamo fans showed up to the stadium and clashed with AEK fans who had gathered there.
Fans from both sides "threw flares, improvised incendiary devices, objects, stones, and also used improvised bats".
Police said a preliminary investigation had started and they were trying to identify the perpetrators.