“Everything is prepared and [the government] will act, if needed, with firmness, proportionality and unity,” a government statement said.
It said caretaker prime minister Pedro Sanchez was meeting with other national political leaders and “he doesn’t rule out any scenario”.
Many people in Catalonia have long fought for it to break away from Spain and become a new European country. Demonstrations have traditionally been peaceful, but not always.
Violent clashes erupted in Barcelona and other Catalan towns after Spain’s Supreme Court on Monday handed nine separatist Catalan leaders lengthy prison sentences for their part in an October 2017 effort to achieve independence.
Rioting broke out on Tuesday evening, when Barcelona police said 40,000 protesters packed the streets near the office of Spain’s government representative.
Protesters turned over metal barriers, set fire to trash cans and threw firecrackers and other objects at police. The outnumbered police used foam bullets, batons and shields to battle the groups amid tense standoffs on Barcelona’s streets.
Pere Ferrer, director of Catalonia’s regional police, said the street violence was “intolerable.”
“The situation is very, very difficult, but the police have the means they need to deal with it,” he told a Barcelona news conference.
An organisation representing downtown Barcelona businesses, called Barcelona Abierta, said the violence in the city had caused “significant losses” and “deeply damaged” the image abroad of the popular tourist destination.
The tumult prompted Mr Sanchez, who is preparing for a general election on 10 November, to consult with his party and other leading figures, some of whom are urging him to take a firmer hand.
Yesterday, thousands of people joined five large protest marches across Catalonia that are due to converge on Barcelona tomorrow.
They included families with children, elderly and young people, and banners reading “Freedom for political prisoners” – a reference to the prominent Catalan politicians and activists leaders sentenced by the Supreme Court.
Feliu, a retiree who walked 12 miles from the northern town of Berga and asked to be identified only by his first name because of the delicate situation in Catalonia, said he didn’t agree with the violence but saw it as a way of gaining attention.
“If foreigners see us protesting peacefully all the time, they might think that nothing is going on or they might not even notice us,” the 68-year-old said.
Catalan regional president Quim Torra joined one of the marches.