Five Manchester United supporters were stabbed and six more arrested as violence flared before the Champions League game with Roma.
It was the second successive season that trouble marred the fixture in the Italian capital.
Rival fans clashed on a bridge, leading to Rome's Stadio Olympico, used habitually by Roma's notorious Ultras - a following of hardcore supporters.
None of the stab victims received serious injuries, while two others, including a 16-year-old boy, needed treatment for being drunk.
Italian media reports said around 50 fans battled with each other as police were forced to wade in with batons to separate them.
The British Embassy in Rome said four Britons were arrested and formally charged with obstructing police officers in their duty. Two others were released without charge.
An embassy spokeswoman said: "Seven Manchester United supporters were taken to hospital and six were arrested after fighting broke out on the Pont Duca d'Aosta bridge which fans cross over the river to get to the stadium."
The embassy had warned travelling fans beforehand not to use the bridge because it was used by the Ultras.
There were no reported disturbances during or after the game which finished in a 1-1 draw.