Hours later in Rome, enraged fans rioted, attacking a police station near the Stadio Olimpico.
Hundreds of youths dragged metal barricades and trash bins to block off one end of a bridge spanning the Tiber near the stadium. They stormed the yard of a police station when a gate was opened for a shift change of squad cars, hurled stones at passing police cars and smashed windows in an attack of the nearby Italian Olympic Committee headquarters near the stadium.
With their faces covered by scarves and ski masks, the rioters also set aflame a trash can at the edge of the bridge, smashed traffic lights and yelled to motorists to turn around and leave the area as the youths roamed across the streets. The rioters smashed a window in the police station and set a police vehicle afire inside the gate.
The stadium was largely empty after security officials in Rome decided to cancel a night match between AS Roma and Cagliari because of fears the Tuscan shooting would enflame fans.
Sky TG24 showed images of flames from what it said was a bus set afire near the barracks. APcom said passengers of a bus that was blocked by the rioting were evacuated and given shelter in the lobby of a building near the barracks.
Rome's police headquarters said that the barracks was under attack but declined to give details saying it was still receiving reports from the field. It said some arrests were made but the number was not immediately available.
ANSA reported that at least 10 police were injured near the Rome stadium, but police said there only a few injuries and they were minor.
RAI state TV, reporting from the stadium, said one of its cameramen was injured as well as a cameraman for a private network.
There were also clashes between fans and police in downtown Milan near the offices of RAI during the afternoon, and about 240 hardcore fans gathered in Milan's central Piazza Duomo after sundown, although they did not engage police, ANSA reported.
More clashes were reported at lower division matches in southern Italy .
In the Tuscan town of Arezzo, about 200 kilometers (125 miles) away, police chief Vincenzo Giacobbe called the fatal shooting of the Lazio fan, "a tragic error."
"Our officer had intervened to avert that scuffle, between two small groups of people who weren't (yet) identified as fans, from degenerating," Giacobbe said in a statement carried by the Italian news agency ANSA. "I express deep sorrow and sincere condolences to the family of the victim."
Gabriele Sandri, a 26-year-old disc jockey from Rome, was hit in the neck by a bullet while in a car at the rest area along the A1Autostrada highway near the town of Arezzo, about 200 kilometers (125 miles) north of Rome. The fans were heading to Lazio's match at Inter Milan.
Arezzo police, reading a statement, said two patrol cars which had stopped on the opposite side of the highway for an unrelated check of vehicles turned on their sirens when they "heard yelling, screaming" and realized the occupants of three cars in the rest area were fighting.
"They turned on their sirens," but the fan clash continued, the police said. "One of the (officers) decided to fire two shots in the air to try to intimidate them.
"At that point the cars moved" to return to the highway, the police said. One of the vehicles "with five occupants, took a shot, which hit the young man in the neck," the statement said.
The car drove a few kilometers (miles) to the nearest exit and asked for help, but the fan had been mortally shot, and an ambulance crew failed to revive him, the police said.
They described the police officer who fired the shots as a veteran but didn't provide the officer's name, and, adding that the case was under investigation, refused to answer questions.
Sandri's brother, Cristiano Sandri, gestured angrily as he yelled "they killed my brother." Flanking him as he got into a car was a man identified by state TV as family lawyer Luigi Conti, who shouted that the shooting amounted to "first-degree murder."
Sky quoted witnesses as saying the other two cars were vans carrying Juventus fans from Naples to a match in Parma .
The Italian soccer federation postponed the Inter-Lazio game to a date to be determined. Sunday afternoon's other games started 10 minutes late, with players and referees wearing black armbands.
The death prompted clashes between fans and police in Bergamo , where AC Milan was playing Atalanta. The match was suspended after seven minutes when Atalanta fans tried to break through a barrier and storm their way onto the field. It will be rescheduled at a date to be determined.
Atalanta captain Cristiano Doni went over to try to calm the fans but to no avail, and both teams headed into the locker room.
Clashes between rival fans at rest stops are common in Italy .
Italian Premier Romano Prodi was attending Mass when he was informed about the death. He described the fan violence as "very worrisome" and later issued a statement saying he has ordered that the shooting be thoroughly investigated.
Last season, a policeman was killed in riots following a game between Palermo and Catania in Sicily . Under new anti-violence measures this season, some fans have been barred from traveling to games.
In 2004, the derby between AS Roma and Lazio was suspended three minutes into the second half when a false rumor spread through the stadium that police had killed a boy outside the stadium, sparking riots.
"We should use shock therapy to sober up the Americans. In this case, the Americans will speak about the need to resume dialogue. There is no other option"
The United States is concerned about the current crisis in the relations with Russia and suggests returning to reasonable policies to avoid a nuclear war