Officers from the Catalan regional police force charged protesters on Friday morning to prevent an invasion of the security perimeter around the venue of the Spanish Cabinet meeting in Barcelona.
The decision by the government to hold its weekly meeting outside Madrid had outraged the separatist movement, which called supporters to join demonstrations outside the meeting's venue, the historic headquarters of the local chamber of commerce, the Llotja de Mar.
The situation was made complicated, said police representatives, due to the violence shown by some of the protesters.
Incidents occurred at various points surrounding the security cordon, Paralelo, Avenida Drassanes, Via Laietana, Raval and Las Ramblas.
The CDR (Committees for the Defence of the Republic) had called for supporters not only to surround the police cordon but also to do their best to bring Barcelona's wider area to a standstill.
At 5.30am demonstrators started blocking traffic and by mid morning roads had been blocked intermittently in all four provinces of Catalonia.
Protesters are expected to come together for a march at 6pm in the city centre.