Hasél was jailed for nine months last week over lyrics and comments deemed insulting to Spain's king and that glorified violence.
Protests in support of a jailed rapper turned violent for a sixth consecutive night in Barcelona on Sunday with clashes between police and groups of youths in the centre of the Spanish city.
It began with a peaceful protest in Barcelona, with graffiti artists painting a mural critical of Spain’s King Felipe VI and his father, former King Juan Carlos I, to show solidarity with rapper Pablo Hasél.
Hasél was jailed for nine months last Tuesday for comments on social media and lyrics that insulted the Spanish monarch and praised violence and terrorism.
As night fell on Sunday protesters mostly dressed in dark clothes marched through the city center to police headquarters, where they pelted police with rocks, bottles, trash and fireworks.
Vandals also broke the windows of shops in the city centre.
More than 100 people, including seven on Sunday, have been arrested during violent clashes with police since Hasél's arrest.
Catalan police said that on Saturday over 35 arrests were made in Barcelona and other nearby towns after rioters smashed store windows and engaged in running battles with police. Other protests across Spain, including the capital Madrid, remained mostly peaceful.