As the Catalan president condemned Spain's "anti-democratic and totalitarian actions", another Catalan leader called for peaceful resistance to protect the buildings as the regional government met in emergency session.
Located in the northeast of the country, Catalonia is recognized as one of Spain's most prosperous regions, not only economically but culturally.
Among the supporters of independence is Manchester City manager Pep Guardiola.
There was no such action taken by the Spanish government before the last referendum in November 2014, however, this time Catalan leaders have revealed that they will declare independence within 48 hours of the final result if there is a majority "Yes" vote.
How did we get here?
Now they have taken a step further in arresting Catalan officials.
The prosperous Catalonia region, whose capital is Barcelona, generates a fifth of Spain's economy.
In August, Catalan parliament passed a referendum law which would be valid from October 1. "The Spanish government is making a grave mistake".
Christine St-Pierre, Quebec's worldwide relations minister, would only say the actions of the Spanish government are "probably not the best thing to do".
On what grounds does the Spanish government oppose the vote? The Spanish government has said the referendum won't happen, but on October 1, many Catalans are likely to try to vote, or at least take to the streets to have their voices heard.
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.
In March this year the former Catalan president Artur Mas was banned from holding public office for two years after being found guilty of disobeying the constitutional court by holding a symbolic independence referendum three years ago.
Nine officials were arrested as part of an operation that is expected to continue throughout the day, a spokesman for the Guardia Civil said.
Spain has been desperately trying to find ballot boxes and papers to seize before the referendum, anything that might prevent it from taking place.
Officers are also searching a Catalan government data center, a press officer for the Barcelona-based executive said in a text message.
In a September 20 speech about recent attempts to prevent the referendum, Catalan President Carles Puigdemont denounced the Spanish government as authoritarian and undemocratic.
An estimated 40,000 people blocked the entrance to the Catalan economy ministry late into the night.
Spanish prime minister Mariano Rajoy said his conservative government is determined to prevent the ballot.
Madrid has also threatened to arrest local mayors who facilitate the vote.
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