Spain's National Court plans to investigate possible sedition charges for demonstrators who took part in a massive protest against a police crackdown on preparations for an Oct. 1 referendum on the Catalonia region's independence.

Investigative Judge Carmen Lamela said Wednesday that the court would investigate if the Sept. 20 demonstration constituted a tumultuous uprising against police, which could constitute sedition. The judge called on Spain's paramilitary Civil Guard to provide information.

The decision followed a complaint by the court's chief prosecutor that named two civil groups as organizers of the demonstration in Barcelona. It took place outside a building that police had raided and two Civil Guard vehicles were thrashed.

The groups, Catalan National Assembly and Omnium Cultural, are two of the driving forces behind the call for Catalan independence.