Violence broke out in the streets of Barcelona on Friday, as more than half a million pro-independence protesters gathered in the Catalan capital.
Spanish Interior Ministry said the clashes left three policemen injured and nine people, including four minors were arrested.
Large scale demonstrations were carried in Spain since Monday night after nine Catalan politicians were handed heavy sentences by the Spanish Supreme Court for their role in an independence movement that tried to separate Catalonia from the rest of Spain two years ago.
Protestors threw objects at the police resulting in a face off with riot police.
Several garbage containers were set on fire, the Barcelona City Council said that 700 bins have been burned during the riots over the past three nights. Trees, pavements, traffic lights and public signs were damaged, with the total cost to the city so far reaching more than €1.5 million or $1.7 million.
What triggered protests?
Protests erupted after the Supreme Court judgment Monday. Oriol Junqueras, the former vice president of Catalonia, was sentenced to 13 years in prison and banned from holding public office for the same amount of time. He was found guilty of sedition and misuse of public funds.
Former Catalan foreign minister Raul Romeva, former Catalan government spokesman Jordi Turull and ex-labor minister Dolors Bassa were convicted of the same offenses and sentenced to 12 years in prison. They were also banned from holding public office for 12 years.
Five other officials and activists were sentenced to between nine and 11 years each, with three more people sentenced for shorter periods of time for lesser offenses.
Their supporters accuse Madrid of political persecution and are calling for another independence referendum, which Madrid calls illegal.
The pro-independence group CDR has called for demonstrators to set up a permanent camp in the city center.