Two law enforcement officers were injured during the Saturday protest, the Askanews news agency said. Anarchists were setting trash cans on fire, breaking shop windows and throwing firecrackers. Several cars were damaged.
The Italian TGcom24 news channel said that five protesters were detained and the identities of 150 protesters were recorded.
Cospito is serving a life sentence for organizing a series of extremist actions. He has been on a hunger strike for months, which has prompted his supporters to stage several protests in Rome, Milan, and Bologna.