Four people, accused of taking part in Rome riots triggered by the accidental killing of a soccer fan by a policeman at a highway rest stop the previous day, were arrested Monday.
The 26-year-old Gabriele Sandri was shot and killed Sunday when a policeman fired a warning shot to disperse a clash between Lazio and Juventus supporters at a rest stop in Tuscany.
Sandri, a disc jockey from Rome, was hit in the neck by a bullet while sitting in a car.
Police said they intervened to stop a scuffle between two groups of people at the rest stop - Sandri's Lazio fans and a small group of Juventus fans. Police had intervened from the opposite side of the highway, where they had stopped for an unrelated check on vehicles.
Sandri's death forced the suspension of three Serie A matches as clashes erupted in Rome, Milan and other cities.
The riots were the latest episode of soccer-related violence in Italy. In February, the death of a policeman at a Serie A game led authorities to tighten security measures in and around soccer stadiums.
The ANSA news agency reported that an autopsy on Sandri's body was scheduled to be carried out later Monday in Arezzo, about 200 kilometers (125 miles) north of Rome where Sandri was killed.
The policeman who fired the fatal shot, whose identity has not been released, was quoted as saying in Corriere della Sera that he did not aim at anyone.
"I was 200 meters (yards) away," he said. "I fired the first shot in the air, and the second went off as I was running."
An earlier police statement said the officer had fired both shots in the air.
In Bergamo where Atalanta hosted Milan, the match was suspended after seven minutes when Atalanta fans tried to break through a barrier and storm their way onto the field.
In Rome, fans rioted into the night, attacking police barracks near the Stadio Olimpico and raiding the nearby Italian Olympic Committee (CONI) headquarters. They smashed windows, hurled stones at police cars and set trash bins and police vans on fire.
Four men were detained in Rome early Monday, police said, while ANSA reported that about 40 officers were injured.
Workers at the CONI headquarters arrived to work Monday morning to find windows broken on the ground level and the floor damaged by a paper bomb set off inside the entrance hall.
CONI president Giovanni Petrucci was set to meet with other officials to address the situation.