Spanish national police have stormed ministries and buildings belonging to Catalonia's regional government to put a stop to the region's independence referendum.

The Guardia Civil, which acts with the authority of Madrid's interior ministry, is searching for evidence regarding the planned 1 October referendum on Catalan independence, which Spain's Constitutional Court has declared illegal.

In the early hours of the morning armed officers arrived at various Catalan ministries, including the economy department, foreign affairs department, and social affairs department, Spanish media reports.

At least twelve Catalan officials are said to have been arrested, including the chief aide to Catalonia's deputy prime minister, Josep Maria Jové. The arrests come as the mayors of Catalan towns who back the referendum were yesterday questioned by state prosecutors.

Pro-independence crowds have formed outside the regional ministries in support of the provincial government and in protest against the raids and searches.

Speaking at lunchtime Carles Puigdemont, the president of the Catalonian government, said the Spanish government had “de facto suspended” home rule in the province.

Catalonia’s elected autonomous regional government, the Generalitat, had called the referendum after pro-independence parties were able to form an administration following elections in 2015.

The president of the province's national assembly, Jordi Sànchez, on Wednesday morning called for "peaceful resistance" to the police operation.

“The time has come. We resist peacefully. We come out to defend our institutions with non-violence,” he said in a post on social media.

On Tuesday police searched for election material including ballot boxes, voting papers and campaign leaflets - raiding private courier companies in the process.

Catalonia referendum protests – in pictures Show all 10 1 /10 Catalonia referendum protests – in pictures Catalonia referendum protests – in pictures Demonstrators block a Guardia Civil vehicle as they try to leave the Department of External Affairs, Institutional Relations and Transparency of the Catalan Government office in Barcelona AP/Emilio Morenatti Catalonia referendum protests – in pictures Demonstrators react as they try to stop the car carrying Xavier Puig, a senior at the Department of External Affairs, Institutional Relations and Transparency of the Catalan Government office, after he was arrested by Guardia Civil officers in Barcelona AP/Emilio Morenatti Catalonia referendum protests – in pictures A demonstrator reacts as he tries with others to stop the car carrying Xavier Puig, a senior at the Department of External Affairs, Institutional Relations and Transparency of the Catalan Government office, after he was arrested by Guardia Civil officers in Barcelona AP/Emilio Morenatti Catalonia referendum protests – in pictures Spokeswoman of the Catalan pro-independence anticapitalist party "Candidatura d'Unitat Popular - CUP" (Popular Unity Candidacy), Ana Gabriel, talks to the media in Barcelona Josep Lago/AFP Catalonia referendum protests – in pictures Republican Left of Catalonia party's (ERC) Member of Parliament Joan Tarda (C) attends a demonstration outside the regional Economy Ministry in Catalonia during a police search for documents connected with the organisation of the Catalan independence referendum, in Barcelona EPA/Alejandro Garcia Catalonia referendum protests – in pictures A man holds pro-referendum poster next to a Spanish Civil Guard who stands in front of the Economy headquarters of Catalonia's regional government in Barcelona. The operation comes amid mounting tensions as Catalan leaders press ahead with preparations for an independence referendum on October 1 despite Madrid's ban and a court ruling deeming it illegal Josep Lago/AFP Catalonia referendum protests – in pictures People hold placards reading "Democracy" as they protest in front of the Economy headquarters of Catalonia's regional government in Barcelona AFP Catalonia referendum protests – in pictures A crowd of protesters gather outside the Catalan region's economy ministry after junior economy minister Josep Maria Jove was arrested by Spanish police during a raid on several government offices, in Barcelona Reuters/Albert Gea Catalonia referendum protests – in pictures People holding 'Esteladas' (Catalan pro-independence flags) attend a protest near the Economy headquarters of Catalonia's regional government Lluis Gene/AFP Catalonia referendum protests – in pictures People demonstrate on a Spanish Civil Guard Police car outside the Catalan Vice-President and Economy office as police officers holds a searching operation inside David Ramos/Getty Images

The Spanish national assembly on Wednesday rejected a motion to support the Spanish government's heavy-handed response to the the referendum by 166 votes against to 158 in favor, after the centre-left opposition party PSOE teamed up with left-wingers Podemos and smaller separatist parties in the parliament.

After news of the raids broke on Wednesday, separatist political parties, as well as Podemos, cancelled all their planned political events for the rest of the day.

"It is unacceptable for there to be political prisoners in a European democracy. The Partido Popular leads us to an authoritarian regression that cannot be tolerated," a spokesperson for Podemos said on social media.

Right-wing parties however endorsed the police operation. Ciudadanos leader Albert Rivera said he supported the raids because the Catalan government had “skipped the law and are trampling our rights”. A spokesperson for the ruling Partido Popular said that “the rule of law is stronger than those outside the law”.