The demonstrators have gathered around Placa d’Espanya along the road that leads up to the mountain Montjuic and the Palau Nacional.
One person, speaking on condition of anonymity, who was attending the rally told Express.co.uk: “It’s packed with people. There are thousands here. Everyone I know wants independence.”
As with past demonstrations the protestors have chanted: “Votarem” (‘We will vote”)
The drive to hold the independence referendum in the north west region has been slowly building in recent days despite the authorities in Madrid ruling the vote to be illegal and against the constitution.
However Catalans have continued to resist attempts by the Prime Minister Mariano Rajoy to prevent the referendum going ahead on October 1.
Earlier today farmers deployed a convoy of tractors – dubbed a ‘Tractorada’ – and drove into the capital Barcelona as a show of support.
In recent days firefighters and lawyers and solicitors have joined the growing protest.
Most recently thousands of students took to the streets to demand their right to vote on whether or not the region should break away from the rest of Spain.
The demonstration comes after the Catalan Interior Minister Joaquin Forn said that he had been informed by the central government’s Ministry of the Interior in Madrid that over an extra 5,000, in total, police and members of the Guardia Civil had been sent to the region as relations between Catalonia and Madrid had worsened.
Catalan President Carles Puigdemont made it clear today that his government is determined to go ahead with independence vote this Sunday despite the actions of Madrid which have plunged the entire country into its worst political crisis in decades.
Mr Puigdemont said: “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.
“I don’t believe there will be anyone who will use violence or who will want to provoke violence that will tarnish the irreproachable image of the Catalan independence movement as pacifist.”
Courts have also ordered police to cordon off schools scheduled to be used as ballot stations. In a bid to keep them open, parents have called for a mass school sleepover this weekend, with tents and sleeping bags, free paella and cinema. Organisers said 60,000 had already registered to participate.
Separatists have called on people to turn out early at polling stations in a mass statement of “peaceful resistance”, even if they are prevented from voting.
Madrid though reiterated its stance that it was determined that the referendum would not take place.
Government spokesman Inigo Mendez de Vigo told a news conference following the weekly cabinet meeting: “I insist that there will be no referendum on 1 October.”
He said organisers would face criminal charges for trying to hold it.