The European Commission said Monday that Catalonia's disputed referendum was "not legal" under the Spanish Constitution and urged dialogue between Barcelona and Madrid in what has become and escalating political crisis in the region's fifth-largest economy.

"If a referendum were to be organised in line with the Spanish Constitution it would mean that the territory leaving would find itself outside of the European Union," the Commission said in a statement. "Beyond the purely legal aspects of this matter, the Commission believes that these are times for unity and stability, not divisiveness and fragmentation."

"We call on all relevant players to now move very swiftly from confrontation to dialogue," the statement said. "Violence can never be an instrument in politics. We trust the leadership of Prime Minister Mariano Rajoy to manage this difficult process in full respect of the Spanish Constitution and of the fundamental rights of citizens enshrined therein."

The Commission's view follows Rajoy's assertion that people in Catalonia were misled into voting in a illegal referendum Sunday and implied that the region's independence movement was a "path that leads to nowhere."

"There was no referendum today," Rajoy insisted during a televised addressed to the nation late Sunday after a day of shocking violence in the northeast region of Catalonia that saw hundreds injured by riot police, who fired rubber bullets on protesters in the capital of Barcelona, during a vote the federal government has declared illegal.

"The responsibility for these acts solely and exclusively falls on those who promoted the rupture of legality and coexistence," Rajoy said "The vast majority of the people of Catalonia did not want to participate in the secessionists' script."

Rajoy added that the vote was a "real attack on the rule of law ... to which the state reacted with firmness and serenity."

Catalan officials have said nearly 800 people were injured over the course of the day, which Spanish police, under orders from the government of Spanish Prime Minister Mariano Rajoy, seizing ballot papers, closing public buildings used as polling station and attempting to quell protests in Barcelona and elsewhere in their effort to prevent the referendum from taking place.

While the referendum is non-binding, it could establish a stronger popular movement towards Catalan independence from Madrid under the leadership of President Carles Puigdemont.

Spain's Constitutional Court has declared the vote illegal and allowed the government, under terms of an agreement arranged in 1978, to suspend Catalonia's regional government and assume control if it declares independence.

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