Thousands of protesters took the streets of Barcelona, Girona and Tarragona in support of Catalonia’s independence from Spain for a second day, leading to clashes with police.
Fires were started and protesters attempted to storm government offices in the regional capital.
The protest was sparked by the sentencing on October 14 of nine Catalan separatist leaders.
A spokesperson for Catalonia’s regional government, Meritxell Budó, said they sympathized and understood the anger of the protesters.
Meanwhile, Spanish authorities say they are investigating who is coordinating the disruption.
Protesters have reportedly been using an app known as Tsunami Democratic, which directs them to protest sites in Catalan cities.
In Barcelona, riot police fired tear gas and charged a crowd of protesters who were trying to access government buildings.
There were three arrests, and local media reported that nine people had been treated by medical services.
Protests were also reported in the Catalan cities of Girona and Tarragona.
Pro-independence leaders – who control the Catalan regional government – say they will keep pushing for a new referendum on secession from Spain.
The protests began after nine Catalan independence leaders were handed jail sentences of between nine and 13 years by Spain’s Supreme Court on October 14.
The separatists were convicted of sedition over their role in an independence referendum in 2017, which Spain said was illegal.
Another three were found guilty of disobedience and fined, but not jailed. All 12 defendants denied the charges.
Joan Tardà, the former deputy leader of a pro-Catalan independence party, has called for peaceful protests.
He tweeted: “There is nothing more lethal to independence than the combination between a violent minority action on the street and an uncontrolled police force.”
On October 14, thousands of protesters blocked roads to Barcelona’s El Prat airport – a major transport hub.
More than 100 flights were canceled as demonstrators fought running battles with riot police at the terminal buildings.
Catalan nationalists have long complained that their region, which has a distinct history dating back almost 1,000 years, sends too much money to poorer parts of Spain, as taxes are controlled by Madrid.
The wealthy region in Spain’s north-east is home to about 7.5 million people, with their own language, parliament, flag and anthem.
In September, a march in Barcelona in support of Catalonia’s independence from Spain drew crowds of about 600,000 people – one of the lowest turnouts in the eight-year history of the annual rally.