Protests in Barcelona turned violent at the weekend as demonstrators clashed with police in the streets of the Spanish city for a sixth straight night over the imprisonment of a popular local rap artist.

The demonstrations began after a Barcelona court sentenced local rap artists Pablo Hasél to nine months in prison over his tweets and lyrics slamming the Spanish monarchy. Hasél was charged with insulting the monarchy and glorifying terrorism.

Protesters have been calling for Hasél's immediate release. His arrest had sparked a national debate over free speech in Spain, including a call to remove the country's so-called "Gag Law," which allegedly infringes on the people's freedom of expression.

Several politicians, artists, and celebrities have openly called for a change in the country's laws. Last week, the government said that it would implement some changes, including the removal of prison terms for offenses involving freedom of expression.

Sunday night's protests reportedly began peacefully just like the previous days. However, tensions between police and protesters escalated as night fell, leading to violent confrontations.

Local media reports said that police and protesters clashed for nearly half an hour, with people throwing rocks, firecrackers, and bottles at heavily geared officers.

The clashes reportedly occurred as the demonstrators, dressed in dark clothes, marched towards the National Police headquarters. Police were forced to respond to the violence by shooting protesters with guns loaded with rubber bullets.

According to authorities, more than 100 people have so far been arrested since the protests began last week.  Police said that they arrested seven people on Sunday and 35 people on Saturday in Barcelona and other nearby towns. So far, other protests in cities such as Madrid have remained mostly peaceful.

Saturday's protests have far been the most violent, with rioters smashing windows and looting stores in Barcelona. No casualties have been reported but several people have been seriously injured - including one young woman losing an eye.

Protesters had set fire to several vehicles along the streets of Barcelona. The Barcelona stock exchange was also set on fire.