Crowd trouble broke out at the San Paolo Stadium today before, during and after the Italian first division match between home favourites and relegation strugglers Napoli and Italian league leaders AS Roma which finished 2-2.
In all 38 people were injured - 23 from the security forces and 15 supporters from both sides.
Two Roma fans had been slightly wounded in stabbing incidents near the stadium, one in the shoulder and the other in the leg.
Before the match the trouble started. More than an hour before kick-off (scheduled 13:00 GMT) some families decided to leave the stadium because of violent clashes.
One Napoli fan said: "It's too dangerous, it's like an urban guerrilla war."
Much of the trouble occurred in the Curva A area of the ground where Napoli fans congregate and seats and other missiles were hurled and at least one Napoli fan was arrested.
Earlier a group of fans wearing facemasks had attacked police near the turnstiles for Curva A.
Inside the ground the Roma fans were housed in a makeshift cage while Napoli fans destroyed toilets inside the ground.
Outside the ground a police car and other vehicles were torched after the match while Roma fans also caused damage at the railway station on the way home.
Some 15,000 fans of Roma had made the trip to Naples even though only 5,000 had tickets. -AFP