A fan was stabbed during skirmishes between Roma and Lazio hooligans ahead of the teams' meeting in the Italian Cup on Wednesday.
According to the ANSA news agency reports, the fan was a teenage supporter and he was stabbed in the buttocks. His condition isn't considered serious after he was taken to the hospital.
Later, a window on Lazio's team bus was broken on the way to the Olympic Stadium in a repeat of the sort of violence that has regularly dogged the fixture.