The European Commission says Sunday's independence referendum in Catalonia was "not legal" but also called on the Spanish government to open dialogue.
A spokesman for the commission, the executive arm of the 28-nation EU, said Monday that "violence can never be an instrument in politics."
The commission said in a Twitter message that "these are times for unity and stability, not divisiveness and fragmentation."
The director of the OSCE Office for Democratic Institutions and Human Rights (ODIHR) IngibjÃ¶rg SÃ³lrÃºn GÃsladÃ³ttir also called on the Spanish authorities to ensure respect for fundamental freedoms of peaceful assembly and expression," in order to facilitate communication and employ "de-escalation measures to reduce tensions."
"The Spanish authorities must ensure that police use force only when necessary and in strict adherence to the principle of proportionality," she said.
Nearly 900 injured
Officials in Catalonia said nearly 900 people were injured when police tried to keep residents from voting. Spain's Constitutional Court had suspended a law passed by the region's parliament calling for the vote, but the referendum was held anyway.
In a televised address after polls closed, Catalonia regional President Carles Puigdemont said Catalonia had "won the right to become an independent state" and urged the European Union to stop looking "the other way."
WATCH: Catalonia President
The government of Spain, however, forcefully disagreed.
Spain will do "everything within the law" to prevent Catalonia from declaring independence, Justice Minister Rafael Catala said Monday in an interview with Spanish public television.
"If anyone plans to declare the independence of part of the territory of Spain, as he can't since he does not have the power to do so, we would have to do everything within the law to impede this," Catala said.
Catalonia's government said early Monday that preliminary results showed that 90 percent of voters in Sunday's referendum want the region to declare its independence from Spain.
Regional government spokesman Jordi Turull said 2.02 million of the 2.26 million votes cast were for independence. He said nearly 8 percent of voters rejected independence and the rest of the ballots were blank or void.
Voter turnout was about 42 percent in Catalonia which has an electorate of 5.3 million voters.
Spanish Prime Minister Mariano Rajoy, who spoke from Madrid Sunday slammed the vote — calling it illegal and an attack on the rule of law.
"At this hour, I can tell you in the strongest terms what you already know and what we have seen throughout this day. There has not been a referendum on self-determination in Catalonia today," Rajoy said.
Puigdemont replied, saying Rajoy was bringing shame on his country.
"The exterior image of the Spanish state keeps getting worse and today they have reached embarrassing levels that will always be always remembered," Puigdemont said.
Police officers from Spain's national police forces raided polling places in an effort to close them down and halt voting. Video showed police dragging people from polling stations and beating and kicking would-be voters and demonstrators.
Puigdemont said he would appeal to the European Union to look into alleged human rights violations in connection with the violent efforts to halt the vote.
IN PICTURES: Catalonia Independence
In a statement issued late Sunday, the State Department said the United States supports a strong and united Spain. The U.S. also supports the right to free assembly, the statement said, and urged those involved to act in a way consistent with Spanish law.
Several labor unions and other organizations called for a strike Tuesday to protest the police crackdown.