Earlier in the day, a rally of the Vox party under the banner "Catalonia for Spain" began in Barcelona, according to the Europa Press news agency.
A number of left-wing organizations, supporting the independence of Catalonia, including the Popular Unity Candidacy and others, opposed the demonstration. They tried to approach the place, where Vox’s rally was being held, but the police blocked their way. The left activists then started throwing rocks at police officers, which resulted in clashes.
The citizens of the Spanish region of Catalonia held an independence vote in defiance of the policies of the central authorities in October 2017. Spain, in turn, doomed the referendum illegal. At the vote, over 90 percent of the voters supported Catalonia's secession from Spain, after which Madrid dissolved the regional parliament and introduced the direct rule over the region.