Catalan pro-independence demonstrators march as they arrive at Arenys de Mar, near Girona, Spain, Thursday, Oct. 17, 2019…
Catalan pro-independence marchers arrive at Arenys de Mar, near Girona, Spain, Oct. 17, 2019. Thousands of people joined five large protest marches across Catalonia that converged on Barcelona.

As thousands of pro-independence protesters poured into the streets of Barcelona for a fourth straight day Thursday, the president of Spain's Catalonia region vowed to push for a new independence referendum within two years.

Quim Torra also condemned the violence that has marred the protests, saying the separatist cause was a peaceful movement.

Catalonia's former regional president Carles Puigdemont, center, holds a banner with others during a protest in front of the…
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Catalan protesters, frustrated by the lengthy prison sentences handed to pro-independence politicians this week, have clashed with police, set fires and destroyed property.

The Spanish Ministry of Interior said nearly 100 people had been injured, almost half of them police officers. More than 95 protesters have been arrested since Monday.

"No criminal activity will go unpunished,'' interim Interior Minister Fernando Grande-Marlaska said Thursday.

The protests began after the Supreme Court sentenced nine pro-independence politicians to between nine and 13 years in prison for their roles in the 2017 referendum on Catalonia's push to split from Spain.

The Spanish constitution states that Spain is indivisible and anyone pushing a split is considered a criminal.

The U.S. Overseas Security Advisory Council has warned Americans traveling to northeastern Spain to travel to Catalonia will likely be disrupted by a general strike that has been planned for Friday. It said travel to Barcelona from surrounding cities would be difficult because of "marches on major highways from Tarragona, Tarrega, Berga, Vic and Girona."  It asked visitors to "exercise caution in the vicinity of demonstrations as they may occur with little or no warning."