Then, shortly after polls opened at 9 a.m., Spanish national forces in riot gear entered several sites, including the high school in northeastern Catalonia where the regionâs leader, Mr. Puigdemont, was expected to vote.
Ada Colau, the left-wing mayor of Barcelona, called on Prime Minister Mariano Rajoy to resign over his âcowardlyâ and unjustified police intervention.
âToday weâre not talking about independence or not, but about a breakup between Mariano Rajoy and his government with Catalonia,â she told reporters.
Overnight, Catalans had used tractors to block police access to some rural municipalities so that the vote could go on. In other places, residents removed the doors of polling stations to ensure that the police could not bolt them on Sunday.
Catalans are voting not only without backing from Madrid, but also without any sign of support from the European Union or other major players in the international community. The vote is happening in makeshift conditions, with a disputed census used as the voting list.
They are relying on privately printed ballots, after millions of them were seized recently by the police. To prevent a shutdown, the Catalan government changed the voting rules an hour before poll stations were scheduled to open on Sunday, allowing Catalans to cast a ballot in any poll station, without using an envelope and whether registered there or not.
Mr. Millo, the Spanish governmentâs representative, said the last-minute change turned what was already an illegal Catalan referendum into âa joke.â
Mr. Millo said the police were ordered to seize election-related equipment and not people, but news channels showed violent altercations. Carles Soler, 52, said he was hurting as he walked barefoot down Carrer Sardenya in Barcelona, after âa police officer hit me from behind.â He added: âMy flips flops didnât resist either.â
As the tensions mounted on the streets, F.C. Barcelona, the soccer club, was considering postponing a match scheduled to take place in its Camp Nou stadium later on Sunday afternoon.
A few outsiders had traveled to Catalonia from other countries to act as observers, saying they wanted to make sure that the police did not use force against voters.