Two days ahead of the planned vote on 1 October, the Spainsh national government has made its biggest, and some would say its most authoritarian move yet to stop it from happening.
Spain’s government said on Tuesday police would take control of voting booths in Catalonia to help thwart the region’s planned independence referendum that Madrid has declared illegal.
Spain's Guardia Civil police have previously detained a dozen senior Catalan officials and raided regional government ministries involved in organising a banned independence vote.
Spain's finance minister, Cristóbal Montoro, said the national government was now set to take control of a large part of Catalonia's public finances.
Tensions were already high when Josep Maria Jové, number two in the Catalan vice-presidency, and others were held.
Catalan leaders are defying a court order to halt the vote, condemned by the Madrid government as illegal.
Spain did not stop an earlier vote taking place in November 2014, but this time the Catalan leadership plans a declaration of independence within 48 hours of a Yes vote. Spain's government has been backed by the Constitutional Court, which has suspended the referendum law passed by the Catalan parliament.
Spanish Prime Minister Mariano Rajoy said the state had been forced to act.
But after an emergency cabinet meeting Catalan President Carles Puigdemont accused the Madrid government of "de facto" suspending the region's autonomy and imposing a state of emergency.
Catalan regional president Carles Puigdemont.
Accompanied by his ministers and speaking from the gothic gallery in the Palaceo of the Generalitat in Barcelona, Mr Puigdemont said Madrid "has crossed the red line that separated it from the repressive governments" and enacted a “de facto suspension of Catalonia's self-government and has de facto applied the state of emergency”.
"It's an unacceptable situation,” he added. “They have violated fundamental rights and the Charter of Human Rights. They have made an illegitimate suspension and intervention of the Generalitat by a Government does not respect the basic principles of democracy.”
He accused Spanish prime minister Mariano Rajoy of having perpetuated a “democratic shame” with his actions and said Spain had broken the EU's charter of fundamental rights, which includes the right to self-determination and autonomy for minority groups.
The Spanish prime minister Mr Rajoy said the regional government had been warned that they were destroying Spain's national sovereignty, "There's no democratic state in the world that would accept what these people are planning," he said. He urged the Catalan president to comply with the law and put his secessionist challenge into "reverse gear".
Some 7.5 million people live in Spain's well-off north-eastern region and a majority are thought to be in favour of having a vote.
However, one survey commissioned by the Catalan government in July suggested that 41% of voters backed independence while 49% were opposed.
Catalan nationalism has been stirred by Spain's economic crisis. While Catalonia is one of Spain's wealthiest regions, Catalans argue they pay more into the national budget than they get back. And a 2010 Constitutional
Court ruling fuelled nationalist anger when it set limits on Catalan claims to nationhood.
In the non-binding 2014 vote, branded illegal by the Madrid government, just 2.2 million voters out of a potential 5.4 million turned out. Officials said 80% of them backed independence.
The big concern for Spain is that if Catalonia does succed and declares indepependece, that will encourage other parts in Spain to do so as well, prompting the disintegration of Spain as a country.