The rally was organized by the Catalan pro-independence groups and trade unions. All the activists were dressed in yellow shirts in solidarity with the Catalan politicians who ended up in jail following the October referendum for the independence of the region. "It is time to build bridges and the Catalan problem can not be solved through the courts but by dialogue and politics", he added. The local authorities estimated that 315,000 people assembled in the Plaça d'Espanya for the midday march, with more than 950 buses bringing in supporters from across Catalonia.
It is not the moment of trials or arrests, but of building bridges and finding a solution, assured the General Secretary of the UGT of Catalonia, Camil Ros.
The demonstration comes 10 days after a German court dismissed an extradition request for Catalonia's ousted separatist president Carles Puigdemont on grounds of rebellion and released him on bail.
Spanish prosecutors last week handed over new information to Germany they hope will prove the use of violence which would justify the rebellion charge against Puigdemont and their extradition request.
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.
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The Supreme Court of Spain prosecuted them for the crimes of rebellion and / or embezzlement of public funds for their role in holding a referendum on self-determination, which led to a unilateral declaration of independence on 27 October.
Alex de Ferrer, a 50-year-old IT specialist, said he'planned to take part in the protest because jailing separatist leaders "only serves to manufacture separatists". "The interpretation of the references to "Catalonia as a nation" and to "the national reality of Catalonia" in the preamble of the Statute of Autonomy of Catalonia have no legal effect", the constitutional court had decreed.
Catalonia has been without a government since late December, when pro-independence parties won another majority in parliamentary elections.
Since October 16 the leaders of Catalonia's two largest pro-independence groups - Jordi Sanchez of the ANC and Jordi Cuixart of Omnium Jordi Cuixart - have been in jail while they await their trial for rebellion.
If a new leader in Catalonia is not elected by May 22, new regional elections will be held.