"Everything is prepared at the more than 2,000 voting points so they have ballot boxes and voting slips, and have everything people need to express their opinion", he said.
The warning comes after a dozen Catalan officials were detained for two days last week.
-2010: Spain's Madrid-based Constitutional Court strikes down key parts of the 2006 charter, inadvertently breathing new life into the secession movement.
Earlier in the day, Spain's Civil Guard entered Catalonia's Center for Telecommunication and Information Technology (CTTI) to switch off the software, necessary to count electronic votes at the independence referendum.
The local government has refused to call off the referendum despite the Spanish authorities attempts to block it.
Authorities in Madrid and Barcelona continued their standoff on Friday (29 September), hours before an independence referendum was due to take place in Catalonia despite having been declared illegal by Spanish judges.
"All polling stations will be in place - even if someone tries to stop it, citizens will still be able to vote", Oriol Junqueras, Catalan economy vice president, said.
"I would not deny that we are nervous because we don't know what is going to happen", said Roger Serra, a parent who spent the night at Enric Casassas primary school here alongside about 50 others.
"We're determined to resist peacefully", said Víctor Mitjans, a 44-year-old public servant who stood with his wife and his child at the gates of a public building in Sortidor square in Barcelona. "Then, if "yes" or "no", it's up to each person".
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Mr Bolton said Ukip had avoided becoming the "UK Nazi Party" after his defeat of Anne Marie Waters. Britain and the European Union are now negotiating the terms of Britain's departure.
In one of the biggest crises to hit Spain since democracy was restored after the death of Franco in 1975, the referendum has pitched the wealthy northeastern region against the central government and sown divisions among Catalans themselves.
More than 5.3 million voters are on the electoral roll, according to the Catalan government.
In Madrid, Barcelona, Sevilla, Santander, Alicante and Valencia, thousands protested for Spanish unity.
The Catalan authorities hope that the presence of a group of worldwide observes, led by Daan Everts, who was the Organization for Security and Cooperation in Europe's former ambassador during the Kosovo independence process, will add legitimacy for the process. "What it's sure is that tomorrow there won't be a binding referendum with guarantees".
He told Italian news agency Ansa the referendum was illegal but that both the Madrid government and the devolved administration in Catalonia needed to reach a settlement on the matter. The national government rejects the vote as propaganda. "I won't resist, but they will have to carry me out", he said.
"I think it's important to talk on a political level" after the vote, he added.
The activities were backed by Regional President Carles Puigdemont, who told the crowd to believe that Catalonia will be taking its first steps as a sovereign nation, a BBC report read.
It has its own language and culture.
While the vote hasn't inspired mass public rallies or viral social media campaigns outside of Spain, it did prompt small demonstrations in Scotland, where many dream of obtaining independence from the United Kingdom.