Italian football fans have reacted violently inside and outside stadiums following the police shooting of a Lazio supporter.
Gabriele Sandri, 26, was shot in what police called a "tragic error" as they tried to stop violence between rival fans at a motorway stop in Tuscany.
A match between Atalanta and AC Milan was stopped as fans and police clashed. There was violence at other games.
Later hundreds of fans rampaged in Rome and there were more protests in Milan.
The worst violence was in the capital, where hundreds of armed fans attacked a police barracks and the Italian Olympic Committee headquarters.
Sunday's late match between AS Roma and Cagliari had been postponed as a precaution but fans wielding rocks and clubs turned up outside the Stadio Olimpico.
Security guards in the Olympic headquarters barricaded themselves in as fans outside smashed windows and burned vehicles as they clashed with police.
The mob blocked off one end of a bridge over the Tiber and ordered motorists to leave the area.
A bus was torched and scores of police were injured.
Fans and police also clashed in central Milan near the offices of the broadcaster RAI.
In Bergamo, where Atalanta were playing AC Milan, police and fans clashed ahead of the match.
The game was abandoned 10 minutes after kick-off, when fans tried to smash down a barrier and force their way onto the pitch.
In Siena, supporters shouted "murderers" at police.
There was also violence at lower league games in southern Italy.
Seven of the top league games started 10 minutes late with players wearing black armbands although atmospheres remained tense.
Italian Prime Minister Romano Prodi called for a full investigation into the shooting and said the violence was "very worrying". ( BBC )