English football fans have been attacked in Italy by knife-wielding Ultras, leaving two seriously injured in hospital, according to reports.
Trouble flared ahead of the Europa League game between Tottenham Hotspur and Lazio in Rome later.
Italian newspaper La Repubblica reported scenes of "urban warfare" erupting on Wednesday night shortly after 1am in the Campo de Fiori with up to 100 "Ultras" - notorious troublemakers - attacking a band of Spurs fans.
Ten were left wounded with two stabbed, one of whom was believed to be critically ill.
A spokesman for Rome police confirmed seven men were injured - five Britons, one Californian and one Bangladeshi. He said a Briton, born in 1987, was severely injured and was being treated at San Camillo.
"A group of about 40 or 50 people in motorcycle helmets or with their faces covered were armed and attacked the group of English football fans drinking in Campo de Fiori square," the spokesman said.
"The more seriously injured seems to be the Briton born in 1987. The American was born in 1982."
The violence is believed to have occurred at the Drunken Ship pub as fans of the north London club were enjoying a drink. Photographs show the pub wrecked.
The newspaper reported the Lazio fans were armed with knives, baseball bats, belts and knuckle dusters and they went on to "destroy" the venue. One witness told the paper: "We feared the worst."
It is believed police made some arrests at the scene. A spokesman for the Foreign and Commonwealth Office confirmed it was investigating.