Spain's interior ministry said on Friday that it was sending more state police to Catalonia to maintain order and make sure a banned referendum on independence does not take place.

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.

The interior ministry has not disclosed how many more police officers it is sending to the region but Spanish media said between 3,000 and 4,000 had already arrived or were on their way.

They would join the roughly 5,000 state police normally stationed in Catalonia and around 17,000 Mossos officers.

“They will be tasked with surveillance of public spaces and maintaining order. They will act in case the illegal referendum is maintained,” the interior ministry said in a statement.

It added that the extra cordon of police deployed will act as a backup for the Mossos, who will remain in charge.

Some are billeted in three ferries rented by the Spanish government and moored in the harbours of Barcelona and Tarragona because of both a shortage of temporary housing and to avoid clashes between protesters and police forces.

The interior ministry has told police in Catalonia that they will not be able to take time off between September 20 and October 5.

The Catalan government earlier this week accused the Spanish authorities of effectively taking over its administration after state police raided its offices and arrested officials, and the finance ministry took control of the local finance department.

The Catalan regional leader Carles Puigdemont on Thursday said taht he would press on with the referendum, flouting a court ban, as tens of thousands gathered for a second day on the streets of Barcelona demanding the right to vote.