Lazio and Roma fans have clashed ahead of their teams' Seria A derby match later on Saturday, according to reports.
The ANSA news agency said that one troublemaker was arrested when around 200 Lazio fans fought with a group of around 100 Roma fans near the Olympic Stadium where the match will take place.
Police used tear gas to separate the groups ahead of the Derby della Capitale which has a history of being accompanied by violence.
First reports said that the trouble started when the group of Lazio fans approached a bar where Roma fans traditionally gather for the match.
Lazio fans are also repeatedly involved in incidents with a fascist connotation. In the run-up to the derby, leaflets were circulating in Rome showing a concentration camp inmate in Roma colours between fascist leaders Adolf Hitler and Benito Mussolini.
Last month, one man was temporarily detained after Lazio fans sang a fascist chant and made fascist gestures in a Munich beer hall ahead of the team's Champions League match at Bayern Munich.
Roma enter Saturday's match in fifth place in the Serie A table, Lazio are six points back in seventh.