NAPLES was under siege as police battled football hooligans ahead of Napoli's Champions League tie with Eintracht Frankfurt.
Cars were set alight and police officers attacked with reports claiming Frankfurt fans were tearing up the city.
Italian journalist reported visiting German thugs had been joined by Atalanta ultras.
Footage appeared to show both sets of supporters attacking police.
In response 800 cops were deployed on the street, with a reported 300 hooligans causing chaos by setting off flares and turning to violence.
One video showed police under attack, with masked assailants throwing chairs at vans and officers.
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There were also reports of Frankfurt's team bus being targeted with missiles.
The clashes came before the Last-16 second-leg tie between the European sides.
Napoli clinched a 2-0 win away in Germany in the first leg.
And the second leg saw Napoli cruise to a 3-0 victory to confirm their progression into the quarter-finals.
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Local authorities had initially banned anyone from Germany from buying a ticket for the clash amid security fears.
However, a legal appeal eventually allowed those born or a resident of Frankfurt to purchase a Champions League tickets.
Arrests and injuries were reported at the first leg amid violent altercations between the sets of supporters.
According to , 400 Frankfurt fans arrived in Naples, with some Atalanta ultras understood to have accompanied them after helping to bypass the restrictions.
The groups are said to have come by train from Bergamo, Salerno and Bari.
And they were greeted by Napoli thugs as a video showed flares being shot at a Frankfurt bus.
Atalanta recently faced bitter rivals Napoli in a near-empty ground as the ultras had been banned due to security concerns.
Napoli captain Giovanni Di Lorenzo released a video before the second leg urging supporters not to engage in any violent behaviour.
He said: "We are having an exceptional season and tomorrow we can make Napoli history if we manage to reach the quarter-finals for the first time.
"We must all try to have a good day without disorder or quarrels with whoever arrives in the city. Not only at the stadium but in the streets, in the squares, everywhere.
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"As your captain, I ask you not to fall into provocations. Let's try to make tomorrow a day of celebration.
"We do not accept any provocation. Everyone in the stadium with serenity and joy."