A gigantic mosaic in the colours of the Catalan flag 'La Senyera', spread out over Barcelona's Camp Nou, left Real Madrid players in no doubt that Sunday's El Clasico was more than just a soccer match.

Although a vital league game between Spain's top two clubs, the clash represented a fierce political tradition between the centralism of Madrid and the rights of the region of Catalonia.

One banner amongst the 98,000 fans read simply: "Freedom for Catalonia".

Calls for greater rights and independence have been claimed since the death of Spanish dictator Franco in 1975 who suppressed the Catalan language and culture but recently it has come to a head with the financial crisis gripping the country.

A feeling persists that Catalonia is funding the poorer areas of the country, especially in the south.

"Real Madrid face a Camp Nou where the atmosphere will be exceptional and the stimulation will not only be sporting but also social and political," said Catalan daily La Vanguardia on Sunday.

"The dream of barcelonismo is to leave their opponents eleven points behind but also that catalanismo demonstrates it is motivated to show its identity."

It is not the first time that sentiments like that but the difference this year is that it is an opinion expressed by a large section of the middle ground.

"We are fed up with being dictated to from Madrid and discriminated against. We want the right to decide for ourselves whether to stay in Spain or be independent," one fan, Jordi, told AFP on the way to the stadium.

Not everyone shared that opinion.

"This match is not Catalonia against Spain; it's just Barca-Real. We should not mix the two things, we have come to watch a football match," said Antonio Ponce.

An estimated 1.5 million people took to the streets of Barcelona in a nationalist march held on September 11 this year, the Catalan national day.

The date symbolises the fall of Barcelona in 1714 during the War of Spanish Succession and where Catalonia was brought under the control of Madrid.

At 17 minutes and 14 seconds into Sunday's game, shouts for independence rang out around the arena.

Regional president Artur Mas called early elections for November 25 after the central government rejected his call for Catalonia to raise and spend its own taxes, saying it has a right to "self-determination".

For many Catalans, Barcelona is the equivalent of a national team.

Under the presidency of Joan Laporta, the club became its most politicised.

On standing down in 2010, Laporta set up his own political party calling for independence.

"Barca is the national team of Catalonia and my objective as president was to promote our interests and fight for our rights," he said.

The current president Sandro Rosell is more of an integrator, but he has been swamped by the strength of public feeling and says that the club will reflect the mood of the people.

Barcelona manager Tito Vilanova has tried to concentrate on football ahead of what is the most politicised el clasico yet.

"There are always Catalan flags and mosaics a lot of the time and this is all part of football. If you want to talk about politics then there are other places for that," he said on the eve of the game.

After the match, which ended 2-2, Vilanova was quick to praise the fans.

"On the atmosphere, I found once again that the Barca fans behaved as they should, getting behind the team and showing their support in a peaceful manner," he said.