If the people of Catalonia vote for independence, Mr Puigdemont has said "from the first minute we will act as a completely independent state". Organizers put the figure five times higher at 80,000.
The Spanish federal government has filed a complaint with the country's Constitutional Court over the Catalan government and parliament approving the law on the referendum.
The internationally broadcast Russian Television, or RT, alleged on September 20 that a "state of siege" has been imposed on Catalonia and dubbed cruise liners chartered to house additional police agents being deployed to the Catalonia as "Ships of Repression".
The spokesman stressed that the referendum had been prepared by the Catalan government "on illegitimate grounds". People will demonstrate and show what they think about this situation.
Courts have ordered police to cordon off schools scheduled to be used as ballot stations. "The picture of millions of people lining up with a ballot paper in their hand will be more impressive".
The boxes and the ballots were found in the municipality of Igualada, near Barcelona, according to the Civil Guard, Sputnik reported.
"Clearly, numerous polling stations will be shut down [by Spanish authorities]", he said.
Lluis Orriols Galve, a professor of politics at the Carlos III University of Madrid, said the government will have "big difficulties" stopping the referendum.
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Currently, the "uncertainty" around the vote and "what conditions it will take place under" mean the referendum isn't anticipated to be a major betting event.
Both sides told Amanpour they're ready to talk, but the divide over the referendum's legality has seemingly produced a wide gulf. Catalonia's leaders retort they have a right to decide their future even if it not allowed by the Constitution.
"The measures we are witnessing are worrying because they appear to violate fundamental individual rights, cutting off public information and the possibility of debate at a critical moment for Spain's democracy", the United Nations human rights experts say.
"We were ordered to forgive and forget the crimes committed by fascists, like torture by the Guardia Civil, but they will come here and try and stop the referendum", he said.
Spanish security operations to thwart a controversial secession referendum in the northeastern region of Catalonia were continuing on Tuesday as online operations rendered over 140 pro-independence web pages inaccessible.
Occupying a vast region of Northern Spain, Catalonia is an economic nerve centre of the Spanish state with some 7.5 million inhabitants.
Lorena Torrecillas, a 27-year-old physiotherapist who passed by the student protest, said she opposed independence because the pro-separatist camp had not explained well enough what the advantages of splitting from Spain would be. "I think it would be foolish not to", he told reporters.