Protests have continued into a third day in Catalonia after the Spanish government warned it will present a "firm, proportional and united" response to any violence on city streets. The warning follows a second night of civil unrest in the autonomous region. 

On Monday, Spain's Supreme Court sentenced nine Catalan separatists to jail sentences of between nine and 13 years for their part in a 2017 independence referendum which the Spanish deemed illegal. Protests swiftly began in Barcelona and elsewhere. 

On Tuesday night, peaceful demonstrations turned into running battles with the police, with protestors lighting dozens of fires and erecting barricades while the police fired rubber bullets. The Spanish government reported 51 arrests and 72 injuries to police officers, while Catalan health authorities reported 256 injuries. 

"A minority is trying to impose violence on the streets of Catalonia," the government said in a statement. "It's obvious that what we're seeing is not a peaceful civic movement, but one coordinated by groups who use violence to upset co-existence in Catalonia."