Six Liverpool fans and one Napoli fan were arrested last night outside Anfield after a series of clashes between rival football fans.
There was a heavy police presence after violent scenes when the teams last met in the Europa League two weeks ago in Italy.
Police say a large number of fans of the Italian team arrived at the game without tickets.
Seven arrests were made after officers tackled several outbreaks of unrest.
A police spokesman said there would be a full review of the incidents and talks with the club to see if lessons can be learned.