ROME (Reuters) - Nine people were injured when a paper bomb exploded during the Turin soccer derby between Torino and Juventus on Sunday, police said.
The bomb -- like a banger with a small explosive charge -- was thrown from the Juventus supporters' end early in the Italian Serie A match at Turin's Olympic Stadium after violence had broken out before the game even began.
The bomb was thrown in response to other objects being hurled by the Torino home fans.
Two Juventus fans and one Torino supporter were arrested over the incident during the match and a further two Juventus fans were detained in relation to disturbances outside the stadium.
Violence flared before the game when 300 Torino fans tried to block the Juventus team bus from entering the stadium compound and threw stones at the vehicle, breaking one of its windows.
Media reports said Torino fans also threw eggs and bottles.
Police in Turin said in a statement that security video had allowed them to identify one suspect who would face charges of causing criminal damage.
"This was a deplorable episode of serious violence," La Repubblica's website quoted Juventus sporting director Beppe Marotta as saying.
Violence is not uncommon at Italian soccer games but authorities have worked hard in recent years to clamp down on trouble.
Italian Interior Minister Angelino Alfano thanked the police for identifying and arresting the fans.
"No tolerance towards the enemies of sport: these hooligans want to ruin a passion, deterring people, families, sportsmen from stadiums," Alfano said in a statement.
Gazzetta dello Sport said on its website that five of the injured people had been discharged from hospital, while the others were being treated for various complaints including grazes, dizziness and ear problems.
Torino won the match 2-1, marking their first victory over their more glamorous neighbours and Serie A leaders in 20 years.
Reporting by Isla Binnie, editing by Mark Meadows