A police van burns during a protest in support of rap singer Pablo Hasel after he was given a jail sentence on charges of glorifying terrorism and insulting royalty in his songs, in Barcelona.
Business organizations and police unions have demanded a firmer government action against the riots.
Supporters of Catalan rapper Pablo Hasel protest in Barcelona.
Hasel's imprisonment has also served to channel growing frustrations over a range of other issues.
There were some clashes between protesters and riot police, with images showing rubbish bins on fire, looted shops and objects thrown at officers trying to disperse the crowd, sometimes using batons and foam projectiles.
News images showed thousands of people marching on some of Barcelona's main streets, shouting "Freedom for Pablo Hasel".