Catalan authorities despite the arrest of a dozen regional government officials and 10 million ballot papers being seized, the vote will take place.
Some members of Rajoy's conservative government have even referred to the standoff as democratic Spain's greatest political crisis since 1981, a failed coup attempt in the country's parliament that came only three years after the official end of Gen. Francisco Franco's dictatorship.
Spain's central government says the planned referendum violates Spain's constitution.
The Interior Ministry says the top prosecutor for Catalonia met on Saturday with officials of the Catalan regional police, the National Police and the Civil Guard in Barcelona to inform them of the request.
A spokesman for Junqueras confirmed the arrest and said that other Catalan government premises were being searched by the agents.
Catalonia, which wants to hold a vote on October 1 to split from Spain, has its own police called Mossos d'Esquadra, though the state police Guardia Civil has quarters throughout the region and often works alongside them.
Around 40,000 people protested outside the Catalan economy ministry in Barcelona as police raided the building and arrested the regional economy minister, Josep Maria Jové.
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Former President Barack Obama made similar comments during his administration when he said the U.S. All North Korea's nuclear tests registered as earthquakes of magnitude 4.3 or above.
Meanwhile, hundreds more pro-independence supporters protested outside a courthouse in the north-eastern Catalan town of Hospitalet de Llobregat to demand the release of the arrested officials.
Catalonia is among the wealthiest regions in Spain, and aggressive police tactics are fueling growing outrage among the population, who see it as an insult.
The reinforcements will join 5,000 state police already based in the region.
Spanish Police vans are parked next to a ferry ship, rented by the Spanish Interior Ministry to house National Police and Civil Guard police officers, at Barcelona port on September 24, 2017 in Barcelona, Spain.
Spain's Interior Ministry says that a state prosecutor has asked for the central government to coordinate the policing efforts to impede the referendum on Catalonia's secession from Spain.
"The state is laying the groundwork to take over the Mossos d'Esquadra".
Whether it's sub-state separatism such as what Scotland's been trying to pull off with the United Kingdom and some forces in Northern Italy have historically advocated for, or superstate separatism such as Brexit and the earlier proposal for a Grexit, European unity is fraying like never before, and Catalonia's upcoming vote might just prove to be the catalyst which reinvigorates this continental trend with a new inertia.