Turin security is being increased for Liverpool's return Champions League leg against Italian giants Juventus.
More than 900 police officers will be at the Stadio Delle Alpi in the wake of Tuesday's fan trouble, which caused the Milan quarter-final to be abandoned.
Police held eight Juve fans after an attack on a Liverpool fan on Tuesday.
But the head of Italian counter- terrorism, Giuseppe Petronzi, told BBC Radio Five Live that police were ready for "the highest level" of risk.
"We have reason for concern, but I'm confident we can manage the situation," he added.
Liverpool chief executive Rick Parry has already urged his fans to be on their best behaviour.
"We are asking all our supporters who travel to Italy to behave with the same respect and responsibility they showed in Liverpool," he said.
"Every fan in Turin should remember they are an ambassador for the club."
But fears about the quarter-final grew after Tuesday's trouble in Milan and also when a number of Juventus fans rejected Liverpool's first-leg apology for the Heysel disaster by turning their backs on it at Anfield.
A total of 39 people died during the 1985 European Cup final between the two sides.
And Petronzi acknowledged that threats of retaliation had appeared on the internet.
"We have paid a lot of attention to what they have written and now we must see if they want to do what they have written," he said.
Juventus supporters are likely to launch objects at Liverpool fans
James Richardson
Italian football expert
"I have good reason to expect that this situation will not happen and if it does, we have the proper tools to avoid a dangerous situation for Liverpool fans or for Italian supporters."
Italian football expert James Richardson defended Turin's record, but said he expected Juve fans to throw things at the visiting supporters.
"There are specific towns in Italy where they have problems of violence, but Turin is not one of them," he said.
"One thing that is almost certain to happen is that Juventus fans will launch objects at the visiting supporters.
"If there is trouble at the Stadio Delle Alpi it usually boils down to flares being thrown towards the area where the visiting supporters have been quarantined by the police."
In the build-up to the game, Liverpool fans have been heeding police advice not to wear their club colours and to stay in designated areas.
And the sale of alcohol has also been banned for a 48-hour period.
Liverpool may have 3,000 fans in Turin and they have been advised not to buy tickets for Juve sections of the stadium.
Meanwhile, Otello Lorentini, founder and president of the Association for Victims of the Heysel disaster, believes the two clubs should arrange a friendly as a more fitting tribute.
"I want a friendly game to take place before the end of the year between Liverpool and Juventus in order to honour the victims of the Heysel tragedy," he said.
"This game would be a significant factor for us, a sign that the world hasn't forgotten."