MADRID -- Spanish police arrested at least 12 people Wednesday in raids on Catalan government offices, news reports said, as national authorities intensified a crackdown on the region's preparations for a secession vote that Spain says is illegal.
It was the first time Spanish authorities have detained Catalan officials since the campaign to hold a vote on Catalonia's independence began to gather momentum in 2011.
The move was the latest spike in tension in the standoff between national authorities based in Madrid and pro-independence Catalans over a planned Oct. 1 referendum. Several thousand Catalans gathered to angrily protest the raids outside government offices in the region's capital, Barcelona.
Some demonstrators sat down in the street to block police cars, while others scuffled with officers. Protests also occurred in other Catalan towns. There were no reports of arrests or injuries.
Catalonia's president, Carles Puigdemont, blasted the police operations as "unlawful" and accused the national government of adopting a "totalitarian attitude."
Police acting on a judge's orders searched 42 premises, including six regional government offices, officials' private offices and homes, as well as three companies in Barcelona, the city's superior court said in a statement. It said some 20 people are under investigation for alleged disobedience, abuse of power and embezzlement related to the referendum.
Police and judicial authorities declined to give further details of the operation, which aimed to halt preparations for the vote, saying a judge has placed a secrecy order on it.
Police confiscated nearly 10 million ballot papers, the Interior Ministry said. Polling station signs and documents for electoral officers were also seized during a raid on a warehouse in a small town outside Barcelona.
The Catalan regional government confirmed Josep Maria Jove, secretary general of economic affairs, and Lluis Salvado, secretary of taxation, were among those arrested. Jove is No. 2 to the region's vice-president and economy chief, Oriol Junqueras.
Spanish Prime Minister Mariano Rajoy said his conservative government is determined to prevent the ballot. He said the Catalan government is going against the Spanish Constitution by holding the vote and that "logically, the state has to act."
"No democratic state in the world would accept what these people are proposing," Rajoy said. His stance has the backing of most Spanish opposition parties.
The constitutional Court has ordered the vote to be suspended as it assesses its legality, but Catalan officials say they will press ahead regardless.
"Today the government of Rajoy has crossed a very dangerous red line," said Jordi Sanchez, president of Catalan National Assembly, a civic group leading the independence drive. "We will do all we can for democracy and freedom to prevail."
The Barcelona soccer team, which is popular around the world, waded into the controversy too. It said it "condemns any act that may impede the free exercise of (democratic) rights" and vowed to "continue to support the will of the majority of Catalan people, and will do so in a civil, peaceful, and exemplary way."
The arrests risked stoking public anger in Catalonia, where pro-independence passions can run high. At the demonstration outside the Catalan regional ministry of economy, protester Charo Rovira said she felt sad at the turn of events.
"Catalonia is practically in a state of siege," she said. She added that the arrested politicians were merely acting according to the will of the people.
Spain's Interior Ministry cancelled time off and scheduled leave for Civil Guard and National Police officers who are being deployed to ensure the ballot doesn't happen. It gave no details on the number of agents involved.
In another tightening of the screw, Spain's Finance Ministry said it has imposed further controls over the Catalan government's finances to ensure no public money is used for the referendum. Finance Minister Cristobal Montoro signed an order late Tuesday that limits new credit and requires central authorities' supervision for every payment of non-essential services in Catalonia, the ministry said.
The measure means that virtually all the Catalan public spending will be in the hands of Madrid. The Finance Ministry took over the direct payment of basic services such as education, health and civil servants' salaries last week.
Puigdemont claimed the central government has effectively ended Catalonia's self-rule. The region, like others in Spain, has broad self-governing powers.
Catalonia represents a fifth of Spain's 1.1-trillion-euro ($1.32 trillion) economy. The region's 7.5 million inhabitants overwhelmingly favour a referendum but are roughly evenly divided over independence.
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Barry Hatton contributed to this report from Lisbon, Portugal.
