Catalan separatists rally in Barcelona to support secession

People shout slogans with an "estelada" flag, that symbolizes Catalonia's independence, painted on their face, during a demonstration calling for the independence of Catalonia, in Barcelona, Spain, Sunday, Sept. 11, 2016. The leader of Spain's powerful northeastern region of Catalonia has said he plans to propose a government-approved binding independence referendum to secede from Spain by next year. Catalonia's separatist leader, Carles Puigdemont, spoke Saturday at a news conference before celebrations of the Catalan National Day holiday, which separatists have used for years to rally hundreds of thousands in support of a new European nation. (AP Photo/Emilio Morenatti) (The Associated Press)

People wave 'estelada' flags, that symbolize Catalonia's independence, during a demonstration calling for the independence of Catalonia, in Barcelona, Spain, Sunday, Sept. 11, 2016. Thousands of people demonstrated in Barcelona to call for the creation of a new Mediterranean nation, as they celebrate the Catalan National Day holiday. (AP Photo/Manu Fernandez) (The Associated Press)

A woman holds an "estelada" flag, that symbolize Catalonia's independence, during a demonstration calling for the independence of Catalonia, in Barcelona, Spain, Sunday, Sept. 11, 2016. The leader of Spain's powerful northeastern region of Catalonia has said he plans to propose a government-approved binding independence referendum to secede from Spain by next year. Catalonia's separatist leader, Carles Puigdemont, spoke Saturday at a news conference before celebrations of the Catalan National Day holiday, which separatists have used for years to rally hundreds of thousands in support of a new European nation. (AP Photo/Emilio Morenatti) (The Associated Press)

Hundreds of thousands of separatist-minded Catalans have rallied in Barcelona to show their support for an independent nation that would break away from Spain, leaving it without its powerful and prosperous northeastern region.

Barcelona police estimated on their Twitter account that about 540,000 people attended Saturday's demonstration in support of a legally-binding referendum on secession.

Spain argues that an independent Catalonia would be ejected from the European Union and left out from using the euro currency.

Catalan National Day has long been used to mobilize the masses in support of secession from Spain, which has said any referendum on the issue would be unconstitutional. The economically powerful Catalonia accounts for 18 percent of Spain's economic output.