Liverpool have warned their supporters in Naples to stay inside their hotels and avoid wearing club colours over fears to their personal safety.
Ahead of their opening Group E clash with Napoli on Tuesday, the Reds issued advice only to travel to the stadium on designated buses and to "remain vigilant" in areas away from the city's port over fears of violence from rival supporters.
Several Liverpool fans were treated for stab wounds when they last visited the city during the 2010-11 Champions League campaign, when reports described Reds fans as being "hunted" by Napoli ultras.
The Premier League club have told travelling supporters that "prior to match-day, (they) should remain in their respective hotels to eat and drink" and "should not congregate (on mass) in public areas and should avoid becoming isolated".
They also said: "Supporters are strongly advised not to wear club colours away from the port area (and) any fans wishing to visit the inner areas of Naples city should remain vigilant and be aware they may be targeted for petty theft, robbery and assault."
Supporters should also "not make their own way to the stadium due to risks to their personal safety. This is applicable even if your hotel is near to the stadium".
Liverpool fans are told to congregate no later than 15:30 at the Naples Marine Terminal for shuttle buses to the stadium, the last leaving no later than 18:30, and they will be held back inside the San Paolo Stadium for at least one hour after the full-time whistle.
Bryan Swanson - Sky Sports News chief reporter in Naples
"Liverpool have been allocated just over 2500 tickets for this game. The vast majority are travelling in this afternoon and the advice to them is clear. There are no shortage of ultras signs outside the stadium. An intimidating atmosphere beckons.
"The Italian authorities say there have been no reported incidents involving football supporters - a view that's shared by Merseyside Police, who are liaising with their Italian counterparts on the ground. So at the moment it is baking hot and trouble free."