A man holds a pro-independence poster next to a Spanish Civil Guard who stands in front of the Economy headquarters of Catalonia's regional government in Barcelona on September 20, 2019 | Josep Lago/AFP via Getty Images Catalan president denounces ‘coordinated aggression’ after Barcelona arrests Authorities raid regional government ministries and arrest aide to Catalan vice president.

Catalonia's president, Carles Puigdemont, on Wednesday criticized "coordinated aggression" by the Spanish authorities "with the aim of impeding Catalans to freely and peacefully exercise democracy on October 1."

Puigdemont released a statement after the Spanish Civil Guard arrested 12 people in Barcelona in an operation to prevent Catalan authorities from holding the independence referendum, Spanish media reported.

Among those arrested were Catalan government officials — including an aide to Catalan regional Vice President Oriol Junqueras — and people linked to the organization of the referendum, which is outlawed by Spain's Constitutional Court.

Spanish police also raided several government offices in Barcelona looking to confiscate election material linked to the referendum.

In his statement, Puigdemont said he had "a clear message" to citizens that "we condemn and reject this totalitarian and anti-democratic attitude by the Spanish state. The government has shown us its intolerant side, which has been displayed throughout a large part of Spain’s political history."

He added that "no other member of the European Union is going through what Catalonia is going through. To all democrats, in and outside of Catalonia, who today feel indignation about the events of these last few hours, the government of Catalonia reaffirms its commitment to them and will always ensure their protection. We will not accept a return to former times and we will not accept them preventing us from deciding on our free and democratic future."

On Wednesday evening, Spanish Prime Minister Mariano Rajoy read out a statement as crowds gathered in Barcelona to protest against the arrests.

The conservative prime minister attempted to deflect Puigdemont’s accusations that the arrests were anti-democratic by accusing the Catalan secessionists themselves of being “radically anti-democratic.”

“It is a totalitarian act,” said Rajoy, calling on the regional government to give up its attempt to hold a vote “that cannot be held.”

“We are still in time to avoid bigger problems,” said Rajoy, adding that he remained open to discussion with the Catalan regional government and to hear their demands in person.

Earlier, Puigdemont convened an emergency meeting with his Cabinet, after which he accused the Spanish government of "crossing the red line that separates authoritarian and repressive regimes."

He called the police raids a "suspension" of Catalonia's autonomy and accused the government of declaring a "de facto state of emergency."

Rajoy justified the police actions in parliament on Wednesday, saying: “The government is doing what it must do. I believe the government is complying with its obligation and I must say we will keep doing it until the end.”

He added: “This is a judicial operation which is being done to guarantee … that the law is respected.”

In response, demonstrators gathered in the Barcelona city center to protest the police action.

Junqueras tweeted Wednesday: "They are attacking the institutions of this country and therefore attacking the citizens. We will not allow it."

Barcelona Mayor Ada Colau also spoke out against the police operation, saying in a tweet that it was "a democratic scandal."

Diego Torres contributed to this report.