The arrest of senior Catalan officials and the seizure of campaign material by the police have undermined plans to hold a referendum for independence from Spain on October 1, according to regional officials.

With the referendum having been declared an illegal act, state police arrested Catalonia’s junior economy minister, Josep Maria Jove, in an unprecedented raid of regional government offices.

As reported by the Reuters news agency, police also raided printers, newspaper offices and private delivery companies in a search for campaign literature, instruction manuals for manning voting stations and ballot boxes.

“It is obvious that we won’t be able to vote as we would have liked,” Oriol Junqueras, deputy head and economy minister of the regional government, told local television TV3. “They have altered the rules.”

According to Reuters, this is the first time the promoters of the referendum had acknowledged their plans were in doubt, although Junqueras said he was convinced voters would still turn out in numbers.

It is not yet clear whether the police operation would be enough to prevent the vote overall or if it could instead bring fresh momentum to the secession campaign.

In a separate report, the BBC noted that Spain’s constitutional court has imposed daily fines of up to €12,000 on top Catalan officials for every day they continue organising a banned referendum.

Six senior officials face fines of up to €12,000, while a further 16 officials could be fined €6,000 per day.

Meanwhile, left-wing trade union CGT called for strikes in October after the scheduled referendum.

Although the referendum itself now looks less likely to take place, the already hostile relationship between Catalonia and Madrid has been exacerbated, says the BBC’s Guy Hedgecoe in Barcelona.

From the European Parliament, the S&D Group President Gianni Pittella and Vice President Elena Valenciano issued the following statement: “The European socialists, as well as the European Union institutions, support constitutional legality and enforcement of legislation. We support the more than 120 socialist majors who believe as we do that democracy can only be guaranteed and institutions can only be protected in compliance with the law.”

Pittella and Valenciano also stressed that any measures and acts taken to defend the legality, under judicial monitoring and by virtue of a court judgement, must have the support of democrats.

“What is at stake is the survival of the democratic system, which cannot be jeopardized by anyone under any circumstances. Spain is a consolidated democratic regime and Catalonia has and must continue to have its own self-government for which this democratic system is guarantor. There are no doubts about that in Europe.”

“We make a general call to maintain calm and peaceful engagement. It is always necessary to comply with the rule of law, in keeping with the limits of proportionality.”