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 for a secession vote in Catalonia began to gather momentum in 2011.
The move was the latest spike in tension in the standoff between authorities based in Madrid and pro-independence Catalans. Almost immediately after the news, hundreds of 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.
Catalonia's President Carles Puigdemont blasted the police operations as "unlawful" and accused the national government of adopting a "totalitarian attitude."
Spain's Europa Press news agency and other media outlets said the raids mostly targeted Catalonia's economic and foreign departments as authorities worked to halt all preparatory moves for the referendum planned for Oct. 1. Police and judicial authorities declined to give details of the operation, saying a judge has placed a secrecy order on it.
The Catalan regional government confirmed Josep Maria Jove, secretary general of economic affairs, was among those arrested. Jove is No. 2 to the region's vice president and economy chief, Oriol Junqueras. Police and judicial authorities declined to give details on the operation, saying a judge has placed a secrecy order on it.
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," Mr. Rajoy said. His stance has the backing of most Spanish opposition parties.
The Constitutional Court has ordered the vote to be suspended as it studies its legality, but Catalan officials say they will press ahead regardless.
Spain's Interior Ministry canceled time off and scheduled leave for Civil Guard and National Police officers who are being deployed to ensure the ballot does not 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.
Mr. 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 ($1.3 trillion) economy. The region's 7.5 million inhabitants overwhelmingly favor a referendum but are roughly evenly divided over independence.
This story was reported by The Associated Press.