A Liverpool fan was treated for minor cuts and bruises after an incident in Naples on Tuesday night.
The man in his 20s was taken to hospital but his injuries were not serious.
"We are aware of an incident involving a small group of Liverpool fans and a small group of males on mopeds last night, Tuesday October 2," said a spokesman for Merseyside Police.
"A male in his 20s was taken to hospital to be treated for minor cuts and bruises and released a short time later. Enquiries are ongoing."
Fans in Naples for Liverpool's Champions League match with Napoli have been advised against wearing club colours and not to use public transport to travel to the match.
The club have organised for dedicated transportation to take supporters in and out of the Stadio San Paolo.