Rome - Rome is on red alert with 3,000 police officers deployed to avoid ugly scenes during Roma's Champions League return leg match against Liverpool at the Stadio Olimpico on Wednesday.

Liverpool supporter Sean Cox, a 53-year-old Irishman, remains in critical condition after being attacked close to Anfield by visiting supporters before last week's semi-final, first leg.

Although Roma on Tuesday showed their support for Cox by wearing shirts bearing the words "Forza Sean" (Come on Sean) during a training session, the situation in the Italian capital remains tense.

Authorities fear rival fans could clash from Tuesday evening when many Liverpool supporters, from a total estimate of 5,000 expected to attend, begin arriving in the Italian capital.

British police are in Rome backing up their Italian counterparts with city authorities saying 1,000 officers are being deployed around the Stadio Olimpico in addition to a further 2,000 throughout the city.

Furthermore, there will be a complete alcohol ban, as well as a crackdown on fake tickets.

Merseyside Police Chief Superintendent Dave Charnock urged fans not to travel to Italy if they do not have tickets.

"If the details on your ticket and passport do not match, you will be refused entry to the ground by Italian authorities," said Charnock.

Liverpool fans have been warned to use shuttle buses and not to leave the Stadio Olimpico on foot.

"Under no circumstances should supporters attempt to walk," the club warned.

The club have also told fans to respect public monuments in the capital, to avoid street drinking which is prohibited, and stay clear of the Ponte Milvio and Ponte Duca d'Aoste, two bridges near the stadium.

Fans have also been told to avoid areas of the north of the city on match day, and to expect a long wait before being allowed to leave the stadium.

Liverpool manager Jurgen Klopp and Roma counterpart Eusebio Di Francesco both appealed for calm, as did high-profile former players from each club, Francesco Totti and Robbie Fowler.

Klopp said in his pre-match press conference: "I think we all have the same opinion that the only fight around the football game is on the pitch.

"It's good that we spoke about it, showed Sean's family our support but I really hope that everybody understood that tomorrow in this beautiful city, with good weather, that everyone can walk to the stadium and look forward to an intense, fantastic and very important football game."

Di Francesco said he stood "shoulder-to-shoulder with Sean Cox and his family".

"I'm against all forms of violence, like we all are here. Every set of supporters has some bad apples, who do things that they shouldn't.

"All over the world, unfortunately, there are those who ruin great evenings like the first leg.

"I hope it's an enjoyable occasion for those coming to the stadium tomorrow, that's what I'm pleading for."

But the bad blood between Roma and English fans goes back decades.

Liverpool's last visit in 2001 was blighted by objects being thrown inside the stadium and stabbings.

English fans who visited for the 1984 European Cup final -- where Liverpool famously beat Roma on penalties -- dubbed the Italian capital "stab city".

Middlesbrough fans were also the victims of knife attacks in 2006, while there was trouble the following year with Manchester United supporters.