Hundreds of thousands of supporters of a unified Spain have filled Barcelona's streets in one of the biggest shows of force yet by the so-called silent majority that has watched as regional political leaders push for Catalan independence.
Political parties opposing a split by Catalonia from Spain had a small lead in an opinion poll published on Sunday, the first since Madrid called a regional election to try to resolve the country's worst political crisis in four decades.
Polls and recent elections have shown that about half the electorate in the wealthy northeastern region, which is already autonomous, oppose secession from Spain, but a vocal independence movement has brought the current crisis to a head.
Spain's central government called an election for December 21 on Friday after sacking Catalonia's president Carles Puigdemont, dissolving its parliament and dismissing its government.
The regional government claimed it had a mandate to push ahead with independence following an unofficial referendum on October 1 which was ruled illegal under Spanish law and mostly boycotted by unionists.
Waving thousands of Spanish flags and singing "Viva Espana", protesters on Sunday turned out in the largest display of support for a united Spain since the beginning of the crisis, underlining the depth of division in Catalonia itself.
The poll of 1000 people by Sigma Dos for newspaper El Mundo, which opposes independence, showed anti-independence parties winning 43.4 per cent support and pro-independence parties 42.5 per cent.
The survey was taken from Monday to Thursday, just as the central government prepared to take control of Catalonia.
Madrid said on Saturday that secessionist politicians, including Puigdemont, were free to take part in the December 21 election.
In a speech at Sunday's unity rally, former European Parliament president Josep Borrell called for voters to turn out en masse in December to ensure independence supporters lose their stranglehold on the regional parliament.
"Maybe we're here because many of us during elections didn't go and vote. Now we have a golden opportunity. This time, nobody should stay at home," Borrell said to cheering crowds.