A referendum that is scheduled to take place Sunday will allow residents of Catalonia, the region that includes Barcelona, to vote on whether to declare their independence from Spain.
The warning comes after a dozen Catalan officials were detained for two days last week.
The Catalan police force is under orders to empty the buildings by early Sunday.
Prime Minister Mariano Rajoy’s conservative government has said any vote on Catalan secession would have to be held across all of Spain, not just in Catalonia.
While independence leaders in Barcelona have called on the European Union to condemn Madrid’s “repressive action”, the European Commission has said they only respect Spain’s “constitutional order”.
“We have achieved what was only a dream, on Sunday we have a date with the future”. “We will carry the Catalan flag’s (red and yellow) colors on the collars of our shirts and in our hearts”.
Catalonia joined Spain when the country was formed, but Catalan culture was suppressed in the mid-20 century under a military government run by Francisco Franco, Sergi Mainer explained to Al-Jazeera news.
Now, whatever happens on Sunday and afterward, he said that “the big question” was whether “the Catalan mindset has changed permanently with regard to relations with the Spanish state”.
In an interview with the Associated Press on Saturday, Foreign Minister Alfonso Dastis said: “What they are pushing is not democracy”.
“We feel occupied by the Spanish police”, 56-year-old interior designer Nuria Gimenez said.
But Carles Puigdemont, the head of the Catalan regional government, has said the referendum will go ahead.
“We must be sure there are lots of people present of all ages”, they said in instructions disseminated on social media.
Barcelona’s Joan Brassa high school, for instance, advertised a series of activities for Friday and Saturday, including movie screenings, football matches and Zumba dance fitness classes.
Polls have shown that support for independence has hovered below 50%, with the vast majority of people approving of the chance to put the issue to a vote. The Guardia Civil were stationed on ships in the port of Barcelona in case they were needed.
Officers have also been seizing items such as ballot papers, while prosecutors have ordered the closure of websites linked to the vote and the arrest of officials organising the referendum.
Spain’s military police also raided Catalan government offices, during which at least 14 junior officials and associates were arrested and nearly 10 million ballot papers were seized.
The remarkable occupation of elementary and high schools, which in Spain serve as polling stations, set the stage for an nearly surreal confrontation between pro-independence Catalans and their central government.
She wanted a referendum to be held under constitutional rules so she could vote “no” and try to keep Spain and Catalonia united.
He said he was not a separatist but believed Spain’s efforts to prevent the referendum going ahead were shameful.