More than 460 people have been injured in Catalonia in clashes with Spanish police trying to prevent a referendum on independence from taking place in the northeastern region, Barcelona's mayor Ada Colau said.
Ms Colau said on Sunday, as mayor of the city, she demands "an immediate end to police charges against the defenceless population".
Police have baton-charged and fired rubber bullets to disperse crowds in Barcelona and other towns and cities.
Videos have showed them beating people repeatedly as they try to confiscate ballots and ballot boxes.
In addition to the protesters and voters injured, Spain's Interior Ministry said 11 police officers have been injured fulfilling judicial orders to prevent the referendum on independence.
Earlier Catalan government spokesman Jordi Turull blamed the violence directly on Spanish prime minister Mariano Rajoy and interior minister Juan Ignacio Zoido.
He said actions by Spanish National Police and Civil Guard forces on Sunday were politically motivated and showed "a clear motivation to harm citizens".
Catalan international affairs director Raul Romeva said regional authorities would appeal to European bodies over Mr Rajoy's government's alleged violations of human rights.
The officers fired rubber bullets while trying to clear protesters who were trying to prevent National Police cars from leaving after police confiscated ballot boxes from the voting centre.
Several people were injured during the scuffles outside Barcelona's Rius i Taule school, where some voters had cast ballots before police arrived.
Catalan officials said 38 people were treated for mostly minor injuries.
Manuel Condeminas, a 48-year-old IT manager who tried to block police from driving away with the ballot boxes, said agents had kicked them before using their batons and firing the projectiles.
Elsewhere, Civil Guard officers, wearing helmets and carrying shields, used a hammer to break the glass of the front door and a lock cutter to break into the Sant Julia de Ramis sports centre near the city of Girona.
At least one woman was injured outside the building and wheeled away on a stretcher by paramedics.
Clashes broke out less than an hour after polls opened, and not long before Catalonia regional president Carles Puigdemont was expected to turn up to vote at the sports centre.
Polling station workers inside the building reacted peacefully and broke out into songs and chants challenging the officers' presence.
Mr Puigdemont was forced to vote in Cornella de Terri, near Girona.
The Spanish government and its security forces are trying to prevent voting in the independence referendum, which is backed by Catalan regional authorities. Spanish officials had said force wouldn ot be used, but that voting would not be allowed.
Spain's Constitutional Court has suspended the vote.
Regional separatist leaders pledged to hold it anyway, promising to declare independence if the "yes" side wins, and have called on 5.3 million eligible voters to cast ballots.
Police had sealed off many voting centres in the hours before the vote to prevent their use.
Others were filled with activists determined to hold their ground.
Spanish riot police forcefully removed a few hundred would-be voters from a polling station at a school in Barcelona.
Daniel Riano was inside when the police pushed aside a large group gathered outside the Estela school's front door.
The 54-year-old said that "we were waiting inside to vote when the National Police used force to enter, they used a mace to break in the glass door and they took everything".
He said that "one policeman put me in a headlock to drag me out, while I was holding my wife's hand. It was incredible.
"They didn't give any warning."
In an effort to overcome myriad obstacles, Catalan officials announced voters would be allowed to cast ballots in any location and could use ballots printed at home, rather than in designated polling stations as previously announced.
Mr Turull also said a group of "academics and professionals" would serve as election observers.
The official electoral board appointed by the regional parliament was disbanded last week to avoid hefty fines by Spain's Constitutional Court.
"We are under conditions to be able to celebrate a self-determination referendum with guarantees," Mr Turull said in a press conference.
"Our goal is that all Catalans can vote."
Tension has been on the rise since the vote was called in early September, crystallising years of defiance by separatists in the affluent region, which contributes a fifth of Spain's economy.
As one of Spain's 17 autonomous regions, Catalonia enjoys ample autonomy but key areas such as infrastructure and taxes are in the hands of Madrid.
Separatist Catalans have long complained of contributing too much to the state while not getting enough in return.
Courts and police have been cracking down for days to halt the vote, confiscating 10 million paper ballots and arresting key officials involved in the preparations.
On Saturday, Civil Guard agents dismantled the technology to connect voting stations, count the votes and vote online, leading the Spanish government to announce that holding the referendum would be "impossible".
Mr Puigdemont condemned the crackdown.
"Police brutality will shame forever the Spanish state," he said as crowds cheered.
But Enric Millo, the Spanish government's representative in the region, said police and National Guard forces acted "professionally" to enforce court orders.
He said any attempt to claim the referendum as valid is doomed.
"Today's events in Catalonia can never be portrayed as a referendum or anything similar," he said.
Spain's Interior Ministry said 11 police officers have been injured fulfilling judicial orders to prevent the referendum from taking place.
The ministry tweeted that the injured included nine National Police officers and two Civil Guard agents.
The ministry posted a video on its Twitter account showing Civil Guard officers jumping into two police vehicles to flee a stone-throwing mob in the town of Sant Carles de la Rapita.