Eleven Manchester United fans were taken to hospital after violence erupted around their Champions League match against Roma in Rome.
Manchester United fans and police clashed during the game
The incident has prompted a vigorous debate amongst football fans, many of whom have e-mailed the BBC about where they think responsibility lies.
Here is a sample of what some of them have been saying.
CHRISTIANO CINOTTI, ROME
I'm a Roma fan and I was in the area on match day.
All I want to say is that the violence was due to a group of ultras from both sides: those people don't care about the game, they are only interested in fighting.
So, don't criticise our city and our fans, try to put an end to this ridiculous 'violent reputation'.
A marvellous football match can be obscured by a minority of idiots from both sides.
In Italy we appreciate English culture.
RYAN TENNANT, ROME
I live in Rome and often go to see Roma play. This is the sort of thing that happens in the ground every week but is not reported.
If what happened in the ground here happened in the UK, we would be thrown out of Europe. Every week at home games, the Roma fans in the Curva Nord will throw bottles, flares and fireworks at the away supporters. The stewards never stop them.
The police have no idea on crowd control. They wear no identification numbers and people just expect this to happen.
The section we were in of official United travel supporters was separated by a one-metre high plastic screen.
The stewards watched as we were abused all the game, especially when Roma scored.
United will get the blame, but this is normal police action here that is always just ignored. Until the international cameras are there, then they blame everybody else.
PAUL GRAHAM, DARLINGTON
I am not surprised one iota to hear about the Manchester United fans' experiences after the treatment we Middlesbrough supporters received last year at the Stadio Olimpico.
The behaviour of the so-called security forces on that occasion was disgraceful and what I have seen here only emphasises the gulf in policing quality and strategy between our two countries.
Reading the BBC report was virtually an echo of our trip to Rome, with the one difference that I didn't see a single missile thrown from the Boro fans' enclosure and there was virtually no retaliatory fighting despite the extreme provocation.
There was, however, a torrent of missiles from the Roma fans with absolutely no reprisal from the police towards their fellow countrymen. As soon as a Boro fan appeared to step out of line, the reaction was massively out of proportion.
All the Boro supporters were frisked and their bags searched on the way into the ground - the police must have ended up with a ton of lipstick, other toiletries and loose change with the amount that was confiscated from fans (as potentially dangerous missiles).
JOHN DIXON, BOGNOR REGIS
My wife and I are in Rome on our honeymoon.
We sat in a bar next to the Vatican and watched the match on TV with the locals.
There was a friendly atmosphere in the bar and we all got on very well.
It is a shame that a minority on both sides felt it necessary to shame their countries and that the police went in so heavy-handed.
Hopefully our honeymoon will not be affected by this.
MARK GILDER, SHEFFIELD
Although the scenes and TV pictures are horrific and the force demonstrated by the Italian police is sickening, I must say, it seems that these riots usually seem to involve English fans.
I have watched Roma at the Olimpico Stadium against Inter and must say it was the best football atmosphere I have ever experienced.
No intimidation or fear and very polite fans and police.
There was the usual business in the stadium of the crowd having a go at each other verbally but there was no violence. I sat amongst Roma fans and didn't feel intimidated. In fact, there were some Japanese fans there too and we all got on.
Police did a lot of strict searching on the way into the stadium - checking banners, etc but we were all subject to that.
Roma won that night and it was like they had won the World Cup - hooters and car horns blaring. I've been at Wembley with my team, Sheffield Wednesday, against Arsenal - that was a great game but the Roma one had the best atmosphere.
Also, even when supporting my local side, there is, these days, an increasing level of aggression at both home and away games and, unfortunately, more and more fans seemingly looking for trouble.
DAN PICKLES, LONDON
I went to Juventus last year with Arsenal.
We were given leaflets to say that there was a total ban on alcohol in Turin on our flight out.
When we arrived we were flanked by riot police from the start then taken to the ground and allowed to stand in the car park outside the stadium drinking.
With home supporters also doing the same. All the local shops were selling alcohol.
The Italian police load the gun and just wait for the fans to fire it then go in heavy-handed.
This would never be allowed in England. If it did we would be thrown out of Europe again!.
MATTHEW MCDERMID, ROCHDALE
I was there last night, absolutely ridiculous, we were on the far side opposite the police, and I still managed to get hit with a baton.
This is disgusting, all I wanted to do was to watch the game and go home. Instead I only watched a little football, so I could keep an eye on my child, and also myself.
If we draw against another Italian side, you can forget it, I am not travelling!
I have a massive bruise on my back where I was struck. Horrendous! Clearly Uefa need to look at this - for the past couple of years when English clubs have travelled to Rome, there is always trouble. They need to look into this!