About 200 soccer fans attacked police barracks in Rome after the accidental killing of a fan sparked violence at stadiums and protests in at least four cities.Inter Milan's match with Lazio was postponed on Sunday and AC Milan's game at Atalanta was abandoned early on after a Lazio fan was accidentally shot dead by a police officer.The Lazio fan Gabriele Sandri was killed by a police officer during clashes with Juventus supporters at a service station near Arezzo, prompting the federation to postpone the San Siro match.The dead man was in a car with other Lazio fans, police said.Outside the city's stadium, fans threw firecrackers and overturned garbage bins, clashing with police.News of the fan's death filtered through to other fans and violence erupted before the Atalanta game with supporters scuffling with police in riot gear.A Lazio spokesman said: "It's shocking and inexplicable. We are still asking ourselves how could something like this have happened. It's a tragedy."The Italian government took stringent measures earlier this year to suppress violence in and around football stadia following the death in February of policeman Filippo Raciti, who died on the margins of the Sicilian derby between Catania and Palermo.The Italian government also created an independent body, L'Osservatorio nazionale sulle manifestazione sportive, to clamp down on football violence.The body has rated some games as 'high risk' and prevented fans from travelling to support their clubs in those encounters, including Saturday's Palermo v Napoli game in Sicily.© Independent Television News Limited 2007. All rights reserved.