The clashes came ahead of United's game against Roma

Five United fans were stabbed during skirmishes between a group of 50 rival fans on Wednesday evening.

Four of the six Britons detained were formally charged with obstructing police officers in their duty. Two others were released without charge.

None of the stabbed fans suffered serious injuries.

Embassy staff said it appeared there were no further disturbances as fans left the stadium after the game, which finished 1-1.

This is something we hoped would not happen Sir Alex Ferguson

The violence flared at the Pont Duca d'Aosta bridge, the scene of many clashes between visiting fans and Roma's Ultras contingent.

Police used two baton charges to disperse the fans during the violence, which was the latest in a series of clashes between supporters of the two clubs.

The last time the two teams met in April, 11 fans were taken to hospital after supporters were beaten by riot police inside the stadium. Three United supporters were also stabbed outside the ground.

Scuffles also broke out outside Old Trafford during the second leg of the tie a week later, with 21 people arrested.

Warnings issued

Greater Manchester Police officers had travelled to Rome before this latest match and had issued warnings to hooligans not to attend.

With the two sides having a history of trouble United manager Sir Alex Ferguson admitted he was disappointed by the scenes in the city.

"This is something we hoped would not happen," he said.

"We wanted a nice quiet night and to be able to go home with no incident. It is disappointing that has not happened.