BARCELONA, Spain — Riot police engaged in a running battle with angry protesters outside Barcelona’s airport Monday after Spain’s Supreme Court convicted 12 separatist leaders of illegally promoting the wealthy Catalonia region’s independence and sentenced nine of them to prison.

Officers fired foam bullets and used batons against thousands of protesters who converged on the airport after the verdict was announced in Madrid. Protesters fought back by throwing objects, spraying dark clouds with fire extinguishers and breaking windows during clashes that lasted into the night.

Regional emergency service SEM said 75 people were treated for injuries at Josep Tarradellas Barcelona-El Prat Airport. Spain’s airport operator, AENA, said at least 108 flights were canceled.

Police also clashed with angry crowds late Monday night in downtown Barcelona. They used batons and sounds similar to the firing projectiles were heard.

Nine of the 12 Catalan politicians and activists were found guilty of sedition and given prison sentences of nine to 13 years. Four of them were additionally convicted of misuse of public funds.

The other three were fined for disobedience. The court barred all of them from holding public office.

All 12 were acquitted on the more serious charge of rebellion, which implied the use of violence, brought by state prosecutors and lawyers for the far-right Spanish party Vox. Vox leader Santaigo Abascal criticized the verdict as too light.

Spain’s caretaker prime minister, Pedro Sánchez, said the outcome of the four-month trial proved the 2017 secession attempt had become “a shipwreck.” Sánchez urged people to “set aside extremist positions” and “embark on a new phase” for Catalonia.

He said he hoped the prison sentences would mark a turning point in the long standoff between national authorities and separatist lawmakers in Barcelona, the Catalonia region’s capital.

Tempers flared after the Supreme Court issued its decision in Madrid, with secessionists taking to the streets, halting some trains by placing burning tires and wood on tracks and blocking roads as well as the airport entrance.

After he was sentenced to 13 years imprisonment, former regional vice president Oriol Junqueras declared that achieving independence for Catalonia was “today closer than ever before.”

But the Catalan separatist movement is going through its most difficult period in years. With a general election scheduled for Nov. 10, its most charismatic leaders are behind bars or abroad after fleeing to avoid prosecution.

The convicted Catalan leaders – most of whom were kept in custody on grounds of a flight risk for nearly two years before the verdict – have grown into powerful symbols for the separatists.

Former regional president Carles Puigdemont, who fled to Belgium in October 2017 with several others when they were summoned to appear in court, said the upcoming general election is an opportunity to show “a massive response of rejection” for the court’s verdict and the “dignity and firmness” of the Catalan independence movements.

Puigdemont spoke in Brussels hours after a Spanish Supreme Court judge issued an international warrant for his arrest.

Andrew Dowling, an expert on contemporary Spanish politics at Cardiff University in Wales, said the sentences are “going to make a bad situation worse.”

“It’s going to create a terrible wound in Catalan society until these people are released,” he said by telephone.

Catalan identity is a passionate issue in the northeastern region bordering France, but elsewhere it has failed to capture the public imagination and, crucially, lacked international support.

At the center of the prosecutors’ case was an Oct. 1, 2017 independence referendum that the Catalan government held even though the country’s highest court had prohibited the vote.

The “yes” side won, but because it was an illegal ballot most voters didn’t turn out and the vote count was considered of dubious value. The Catalan Parliament, however, unilaterally declared independence three weeks later, triggering Spain’s worst political crisis in decades.

The Spanish government stepped in and fired the Catalan regional government, with prosecutors later bringing charges.

Catalonia has the authority to run its own prisons, unlike the rest of Spain’s regions. That means regional authorities can allow inmates to spend the night in prison Monday-Thursday and have the rest of the time at home. Such a step for those convicted Monday is open to legal challenges, however.

“Today, they have violated all their rights. It is horrible that Europe doesn’t act,” 60-year-old civil servant Beni Saball said at a Barcelona street protest, referring to those convicted.

But retired 73-year-old bank clerk Jordi Casares said he wasn’t surprised by the verdict.

“It is fair because they went outside the law,” he said, walking out of his home on a Barcelona street. “I hope that after a few days of tumult by the separatists the situation can improve.”

Spain’s caretaker foreign minister Josep Borrell, soon due to become the European Union’s top diplomat, urged an effort at political and social healing because the independence effort is doomed.

“There is no single constitution of Europe that provides the possibility of creating unilaterally the independence of a part of the territory,” he told The Associated Press.

In their ruling, the seven Supreme Court judges wrote that what the Catalan leaders presented as a legitimate exercise of the right to vote was in fact “bait” to mobilize citizens and place pressure on the Spanish government to grant a referendum on independence.

The trial featured more than 500 witnesses, including former Prime Minister Mariano Rajoy and 50 nationally televised hearings.

Defense lawyers argued that the leaders of the secessionist movement were carrying out the will of roughly half of the 7.5 million residents of Catalonia who, opinion polls indicate, would like the region to be a separate country.

The other half of Catalans who oppose independence say the secession question has monopolized local politics and caused friction between families and friends.