According to the Mossos d'Esquadra, 72 of the 128 detainees were minors. Two of those arrested had previous convictions for public disorder. The police force said 220 officers were deployed to control the situation, and 14 were hurt, four of them seriously.
The unrest began in the late afternoon, with groups of young people, many dressed in black and wearing hoods, vandalising street furniture. Riot police moved in, triggering skirmishes through adjoining streets. Protesters threw stones and other objects at officers, erected barricades, and set waste bins on fire. Around 14 shops were looted and 23 vandalised, according to local reports. The fire service responded to 33 incidents of burning street furniture.
The protest came under the banner of an 'International call for a strike and student and youth demonstrations', echoing recent youth-led protests in France and Italy. Earlier in the week, police had been monitoring youth groups circulating the call on unofficial channels. The authorities said they had received no formal notification of the rally.
Catalan president Salvador Illa condemned the violence. 'Violence has no place in Catalonia. Ever. Protesting is a democratic right. Assaulting people, intimidating them and causing damage is not,' he said.
Barcelona mayor Jaume Collboni said the city council would join legal proceedings to seek accountability for the damage. 'This will not be left as it is. We will go all the way,' he warned, adding that there could be consequences for the parents or legal guardians of minors involved.
Catalan interior minister Núria Parlon described the incidents as 'gratuitous violence and vandalism' and said those responsible were not defending any legitimate cause. Both Illa and Parlon stressed that the unrest was separate from the weeks-long housing rights encampment that has been set up in Plaça de Catalunya.