The country's central government vowed to stop its northeastern region breaking away from Spain after Catalonia's leader claimed that 90 percent of voters backed independence in Sunday's referendum, which Madrid says is unconstitutional and a "farce".
Abroad, the focus was on the violence which saw riot police move in on polling stations in towns and cities across the region to stop people from voting, in some cases charging with batons and firing rubber bullets to disperse crowds.
"We call on all relevant players to now move very swiftly from confrontation to dialogue. Violence can never be an instrument in politics," European Commission spokesman Margaritis Schinas said, breaking weeks of virtual EU silence on the Catalan issue.
UN rights chief Zeid Ra'ad Al Hussein said he was "very disturbed" by the violence and urged the Spanish authorities to ensure a thorough and impartial investigation, while EU President Donald Tusk urged Madrid to avoid "further use of violence".
The European Parliament will hold a special debate on Wednesday on the Catalonia referendum, the head of the assembly said.
Residents in many cities briefly stopped work at midday Monday and descended onto the streets in silent, solemn protest.
In Barcelona, municipal police said about 15,000 people stopped traffic as they rallied, many draped in the blue, yellow and red Estelada flag used by Catalan separatists, shouting "the streets will always be ours."
"This was the norm under Franco!" the crowd chanted, referring to former dictator Francisco Franco whose 1939-75 regime repressed Catalan language and culture.
And the main labour unions of Catalonia called for a general strike Tuesday, which could disrupt flights and trains as well as the city's port operations, saying they "vigorously condemn" the violence.
The city's public universities are expected to join the strike, as is the contemporary art museum and the FC Barcelona football club.
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Emergency talks
The government of Prime Minister Mariano Rajoy was holding emergency talks after Catalan president Carles Puigdemont declared Sunday that the region -- which accounts for a fifth of the nation's GDP -- had "won the right to an independent state".
Puigdemont appealed for international mediation to help solve the crisis, and hinted he might be willing to drop the independence drive if that happened.
He also called for all police deployed to Catalonia from other parts of Spain for the vote to be removed.
The regional government said 2.26 million people took part in the vote, or just over 42 percent of the electorate in Catalonia.
But any attempt to unilaterally declare independence is likely to be opposed not just by Madrid but also a large section of the Catalan population, a region of 7.5 million people which is deeply split on the issue.
Rajoy reiterated his government's position that the vote was an illegal act, to which the state had reacted "with firmness and serenity".
Puigdemont has said he will now present the results to the region's parliament, in which separatist lawmakers hold a majority, which has the power to adopt a motion of independence.
Dragged by the hair -
Several top figures in the far-left party Podemos called for Rajoy to resign over his handling of the crisis.
Shocking videos posted on social media showed police dragging voters from polling stations by their hair, throwing people down stairs and attacking Catalan firefighters protecting polling stations.
Puigdemont said close to 900 people had received medical attention, though Catalan authorities confirmed a total of 92 injured.
Four were hospitalised, two in serious condition -- a 70-year-old man had a heart attack and another man was hurt in the eye.
'Institutional crisis'
The Catalan situation is considered Spain's biggest political crisis since an attempted military coup d'etat in 1981.
While Spanish newspapers were unanimous in criticising Puigdemont for pushing ahead with the referendum despite a court ruling it unconstitutional, they also took aim at Rajoy's handling of the crisis.
Rajoy was to hold talks later Monday with the leader of the main opposition Socialist party, Pedro Sanchez, as well as Albert Rivera, the leader of the centrist party Ciudadanos, his minority government's ally in parliament.
Justice Minister Rafael Catala said the government could invoke Article 155 of the constitution, which would allow it to suspend the powers of Catalonia's regional government in order to block any declaration of independence.
"That is a tool that is there... We have always said that we will use all the force of the law, all the mechanisms that the constitution and the laws grant the government," he said in an interview with public television.
The euro and the Spanish stock market slid on Monday after the vote, with bank shares hit particularly hard.
