A 350,000-strong pro-independence protest on Saturday ended in violence as militant elements within the movement clashed with police, turning the streets of Barcelona into a battleground.
Projectiles were fired and at least six people were hospitalised with injuries as barricades were set alight after officers charged ranks of demonstrators - many young and masking their faces - who had amassed outside Spanish police headquarters.
The violent standoff in the city's tourist heartland offered stark evidence of the faultlines developing between hardline and conciliatory elements within the region's independence movement.
It lasted several hours before protesters dispersed through the city's streets.
Earlier, hundreds of thousands of Catalan separatists rallied to demand independence from Spain and calling for separatist leaders to be freed from prison.
The Catalan capital has witnessed daily rallies since October 14th, when Spain's Supreme Court jailed nine politicians and activists.
They were given sentences of up to 13 years for their role in a failed independence bid in 2017.
Meanwhile, city mayors from across Catalonia demanded that they be allowed to map out their region's political future.
Addressing a party rally in Tenerife on Saturday, acting Prime Minister Pedro Sanchez called last week's unrest in Barcelona last week "an attack ...on Catalan society".
Pro-secession activist Jordi Cuixart told Reuters on Friday that in condemning him and other separatists to long prison terms the country was effectively criminalising all dissent against the state.
Catalans remain split over the issue of independence and pro-Spain supporters are due to hold their own rally in Barcelona on Sunday.