It is estimated that more than 300.000 people participated in the protest.
Around 350,000 demonstrators clogged several main city arteries waving flags and wearing yellow in support of separatist leaders jailed for their role in the region's banned drive to split from Spain past year.
A massive march toured today the center of Barcelona demanding the release of nine imprisoned secessionist leaders, accused of rebellion by the Spanish justice system, and favoring a political solution to the conflict in Catalonia.
Organisers of the demonstration which include the two main Catalan independence parties as well as regional branches of two major Trade Unions believe that some 750,000 people attended the rally and once again the streets of the city were awash with yellow and red as well as Catalan flags.
"But it is not a separatist protest".
The Catalan sections of CC.OO. and UGT defended their attendance to the mobilization, after considering that the serious dispute in the rich autonomous community of 7.5 million inhabitants must be resolved through dialogue and politics and not in the courts.
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A German court ruled that he could not be extradited to Spain on rebellion charges but is still considering an extradition on charges of corruption.
Separatist lawmakers defied court orders and held an ad-hoc referendum on independence in October.
Prosecutors say the two men played central roles in orchestrating pro-independence protests in September in Barcelona during which national police were trapped inside a government building for several hours and their vehicles were destroyed.
Alex de Ferrer, a 50-year-old IT specialist, told Agence France Presse (AFP) that he had made a decision to join the protest as jailing separatist leaders "only serves to manufacture separatists". Their subsequent declaration of independence for the region led to a crackdown by Spanish authorities acting to defend the Spanish Constitution, which declares the nation "indivisible".
Seven other Catalan separatist leaders are in jail in Spain while they await trial for rebellion, along with the two leaders of the grassroots separatist groups. The poll surveyed 1,200 people and had a margin of error of 2.8 percent. If a new leader is not named before the end of May, Catalonia will be forced to call another election.