The attack on Tottenham supporters happened at Rome's Drunken Ship pub.
Bar co-owner Gabriele Cianella said the attackers had thrown pieces of iron at the windows and were wearing knuckle dusters.
I think this is the first time that something so bad has happened. We have had other incidents like this but this is the worst.
If you throw stones and knuckle dusters I think you want to hurt someone. There was a lot of blood inside on the floor.
Now we also have some blood on the windows. They came here to hurt someone.
More top news
Chelsea won the first domestic trophy of the season thanks to a 2-0 win over London rivals Spurs at Wembley.
An online video showing a naked man apparently falling down the outside of Buckingham Palace has split opinion online - is it a hoax?
A new market has started up in London championing the production of sustainably produced, local food.