Several hundred people gathered on Monday for a sitting protest in front of the Spanish government delegation building in Barcelona.
The protesters have brought placards reading "Spain: sit and talk", are singing Bella Ciao and demanding the jailed Catalan politicians be released.
The rally, which is being held amid Spanish Prime Minister's Pedro Sánchez visit to Barcelona and organised by the TsunamiDemocratic movement is being guarded by the police, while roads near the protest site have been partially blocked.
Since the beginning of last week, Catalonia has been engulfed in public unrest. Mass demonstrations were sparked by a ruling of the Spanish Supreme Court to sentence nine Catalan politicians, involved in organising the 2017 independence referendum, to 9-13 years in prison on sedition charges and three others to fines for disobedience.
According to the mayor's office, quoted by the news agency Efe, the overall damage caused by the protests has exceeded 2.5 million euros (about $2.8 million).