Ten supporters of English soccer club Tottenham Hotspur were injured, one of them seriously, during an attack in Rome in the early hours of Thursday ahead of a Europa League match against Serie A side Lazio, police said.
The 10, nine British and one American, were attacked outside a pub near the centre of Rome by dozens of masked men. One suffered injuries to an artery and is in a serious condition.
The match ended 0-0 but a group of Lazio supporters chanted "Juden Tottenham, Juden Tottenham" when the game got underway and unfurled a banner saying "Free Palestine".
Tottenham have a large contingent of Jewish supporters while Lazio have long had fans with extreme right-wing sympathies.
"We will have to wait and see if there is anything to act upon," Tottenham coach Andre Villas-Boas told reporters. "If there is, UEFA have to act."
European football's governing body UEFA fined Lazio 40,000 euros last month for racist chanting directed at black players in a match against Tottenham in London in September.
A local resident who witnessed the violence outside the pub earlier on Thursday and called the police said the assailants appeared to have planned the attack.
"The Italians were very organised, with helmets, bats, even balaclavas. There were much fewer of the English," Giuseppe Tamborra said.
"I saw four people lying on the ground, one with his forehead cut open from here to here, probably with a stool taken from the bar."
The attack took place at the Drunken Ship, a popular tourist pub, which was left wrecked by the fight according to photographs published in Italian sports daily Gazzetta dello Sport which showed piles of smashed and overturned bar stools and a pool of blood on the cobblestones outside.
Commenting on their Facebook page the American owners of the bar, located in the central square of Campo dei Fiori, called the incident a "tragedy" and said they would consider claiming damages.
Italian newspaper La Repubblica described the scene as "urban warfare" and said up to 100 Lazio 'Ultras' -- hard core fans of the club -- had attacked the pub.
However, police said that among 15 Italians detained were two fans of AS Roma, Lazio's bitter city rivals, who were charged with violence and grievous bodily harm.
Lazio issued a statement saying any suggestion that the assailants were Lazio supporters was "totally groundless".
It said the episode was "pure delinquency" that had nothing to do with football and called for those responsible to be punished.
Some Italian media reports said the attack may have been politically motivated given the politics of many Lazio supporters, while many fans of the north London side claim a Jewish identity for the club, some referring to themselves as the "Yid Army".
Tottenham fan Dave Illesly said he had left the bar shortly before the violence started.
"That is the trouble with football you never know, when you come abroad to foreign countries trouble comes to you," Illesly said.
Photograph: Yara Nardi/Reuters