Catalonians enraged over the imprisonment of separatist leaders are presenting Madrid with one of its biggest challenges in months. The latest violence came as protesters began a three-day march to the regional capital.
Acting Prime Minister Pedro Sanchez said the government would be firm in stamping out the unrest, which has left dozens injured and arrested over the past three days.
"The Catalan people and all of Spanish society must know that the government is considering all scenarios," Sanchez told a news conference in Madrid.
The latest violence came despite calls from Quim Torra, the leader of the Catalonia region, for protesters to remain peaceful.
"We condemn violence," he said on television. "We cannot let these incidents happen in our country. This has to stop right now."
He had earlier come under criticism from lawmakers in Madrid for not condemning the violence.
"What it is important here is to see these people rejecting the sentences," Torra said while participating in the protest march near the separatist stronghold of Girona. "It's fantastic to see the people mobilizing."
The rolling violent protests came as pro-independence demonstrators set out from five cities across Catalonia on Wednesday and are set to converge on Barcelona on Friday. Organizers expect tens of thousands to rally in Barcelona.