Thousands of students took to the streets of Barcelona and other cities in Catalonia on Thursday to demand the right to vote in the referendum on independence slated for Sunday, which the central government wants to block.

A two-day strike by university students and teachers began in the morning and was widely observed, with two marches taking place in central Barcelona.“It’s just about putting a question to a people who, for a long time, have felt different from the rest of the country,” said Mar Cort, a fine-arts student who was outside Barcelona University, where the marches began.

“We want to separate from the Spanish government. The Spanish people aren’t to blame.”

The central government says the referendum was illegal and, along with the courts, it has been taking legal, financial and other measures to prevent it.

Fourteen arrests were made in regional government buildings last week, prompting the ongoing wave of protests. The Spanish government has also taken control of part of the Catalan regional finances and threatened legal action against more than 800 mayors who have offered their support to the vote.

Older people also took part in the demonstrations, such as Rafaela Gil de Ares (82), who wore a Catalan independence flag badge and matching wristband.

“They never believed that we’d reach this extreme,” she said. “We’re under a dictatorship again. It’s happening all over again. They’re invading us,” she added, referring to the thousands of police reinforcements who have been deployed to Catalonia in recent days, ahead of the vote.

Torn Catalan police

As the referendum date approaches, the roles of the different police forces have come under scrutiny. The Spanish government has put the Catalan regional police, the Mossos d’Esquadra, under the command of the civil guard – and effectively the central government – for the day of the referendum. The Mossos, who normally answer to the Catalan government, have been ordered to evacuate and cordon off schools due to be used as voting stations on Sunday.

However, Joaquim Form, the head of the Catalan interior department, on Thursday said that the Mossos’s priority was “to safeguard civic co-existence”, suggesting that they might resist obeying orders from Madrid.

“We don’t know which side the Mossos are on – if they’re on our side or under the orders of the civil guard and the government,” said Mar Cort. “We don’t know.”

The Spanish secretary of state for security, Antonio Nieto, insisted that the Spanish government prioritises “legality, the rule of law and maintaining co-existence in Catalonia”.

Students wear Catalan separatist flag during a demonstration in favour of the banned independence referendum, in Barcelona. The graffiti reads “We will vote!” Photograph: Jon Nazca/Reuters

Seized ballot papers

On Thursday the civil guard continued to search for material suspected of being linked to Sunday’s vote, seizing 2½ million voting slips and four million envelopes from a warehouse. In another raid 100 ballot boxes were seized, although the company whose premises they were taken from said they had been used for an election at Barcelona Football Club in 2015.

Catalan president Carles Puigdemont sought to reassure head teachers who wanted to allow their schools to be used to stage the referendum, saying his administration would take full legal responsibility.

A civic group called Open Schools has also been campaigning for schools to be allowed to be used for the vote. “We’re not doing a show, we’re holding a protest: we are exercising popular sovereignty and helping the Catalan government hold the referendum,” the organisation said in a manifesto.

The Office of the United Nations High Commissioner for Human Rights issued a statement on Thursday calling on Spain to ensure that its measures ahead of the vote “do not interfere with the fundamental rights to freedom of expression, assembly and association, and public participation”.