A Tottenham Hotspur supporter has been seriously injured, and nine others hurt in clashes with rival fans in Rome.
Spurs are due to play Lazio in the Italian capital later in a Europa League match, and hundreds of their fans are in the city.
The Gazzetta dello Sport newspaper reported the Spurs fan was seriously injured in a bar brawl.
Nine of the injured fans are believed to be British and the 10th is American.
One of the men is believed to have suffered a serious injury to an artery.
The BBC's Rome correspondent, Alan Johnston, reported that police say 30 people - armed with iron bars and with their faces covered - approached the bar where the English fans were drinking in the early hours of Thursday and fighting broke out.
Our correspondent said the bar was wrecked and five people were arrested.
All of them were Italians who the police believe to be Lazio fans.
Some Lazio supporters have in the past been associated with fascism - the club was supported by Mussolini before the war - while Tottenham have traditionally drawn support from the Jewish community.
Some Spurs fans refer to themselves as the "Yid Army", and earlier this year Peter Herbert, chairman of the Society of Black Lawyers, threatened to report them to the police.