About 400 people participated in an unauthorized demonstration in support of anarchist Alfredo Cospito on Saturday, the Italian Rai News 24 TV channel said.
Cospito, who is serving a life sentence for organizing a series of extremist actions and who had been on a hunger strike for months, has been transferred from the Opera prison in Milan to a city hospital, according to local media reports.
On Saturday, protesters in Milan damaged cars and shop windows and threw bottles, rocks, smoke grenades and firecrackers at law enforcement officers, according to Rai News 24 TV. Police used tear gas to disperse the protesters.
At least 11 people were detained after the unauthorized demonstration and six police officers were reportedly injured.
The Saturday demonstration was the latest protest held by anarchists in Milan. All of the protests ended in clashes with police.