Seventy-three of those arrested were minors, with the reports due to be sent “to the juvenile prosecutor’s office”, Catalan police chief Silvia Cata told Spain’s 3CatInfo media outlet.
Footage on social media showed groups of young people, many clad in all-black, attacking businesses in Barcelona after gathering in the city centre for a rally that had not been declared to the authorities.
The scenes come at a time when countries across Europe have been grappling with unrest, with France, Italy and Albania all seeing protests give way to incidents of looting and violence.
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Cata said that only two of the 128 people detained in Barcelona had prior criminal records, and said that a total of 15 officers had been injured during the night.
“This is gratuitous violence,” the police chief said.
While the movement was “completely disorganised”, the call to rally had spread “on social media”, Cata added.
The police were attempting to “study the profile” of those in custody, she said.
