Some incidents of fighting have occurred in the build-up and during tonight's Champions League quarter-final match between Roma and Manchester United, according to Italian media reports.
It has been reported that five people were injured in skirmishes between supporters on the way to the Olympic Stadium.
Three were thought to be English, one from Rome and the fifth a member of the security forces.
The trouble reportedly occurred near two bridges - the Ponte Milvio and the Ponte Duca d'Aosta.
Manchester United fans and Italian police clashed during the halftime break at the Olympic Stadium.
The trouble started a minute before halftime, when Rodrigo Taddei put Roma ahead and the rival supporters started to trade insults and throw objects from one section of the ground to the other.
As United supporters surged towards the barrier separating them from Roma fans, the police intervened with truncheons, setting off scuffles inside the visitors' section.
TV pictures showed one dazed fan with blood pouring from his face with others trying to help him back to his feet.
Meanwhile, announcements were made over the public address system threatening to halt the game.