Police clashed with angry protesters in downtown Barcelona as well as outside the airport after Spain's Supreme Court convicted 12 separatist leaders of illegally promoting Catalonia's independence.

Police fired foam bullets and used batons against demonstrators, and regional emergency service SEM said 53 people were treated for injuries at the Josep Tarradellas Barcelona-El Prat Airport. In downtown Barcelona, police used batons and sounds similar to the firing projectiles were heard.

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Police officers clash with demonstrators outside El Prat airport in Barcelona, Spain, Monday, Oct. 14, 2019. Riot police have charged at protesters outside Barcelona's airport after the Supreme Court sentenced 12 prominent Catalan separatists to lengthy prison terms for their roles in a 2017 push for the wealthy Spanish region's independence. (AP PhotoEmilio Morenatti)

Police clashed with angry protesters in downtown Barcelona as well as outside the airport after Spain's Supreme Court convicted 12 separatist leaders of illegally promoting Catalonia's independence.

Protesters use makeshift barricades during a demonstration at El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Angry demonstrators halted some trains by placing burning tires and wood on tracks, and blocking roads as well as the airport entrance.

Police is surrounded of smoke after protesters used a fire extinguisher during clashes at El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Police is surrounded of smoke after protesters used a fire extinguisher during clashes at El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Protesters block El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Protesters block El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Protesters stand behind a banner reading in Catalan, "Freedom for Political Prisoners" at El Prat airport in Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday convicted 12 former Catalan politicians and activists for their roles in a secession bid in 2017, a ruling that immediately inflamed independence supporters in the wealthy northeastern region. (AP PhotoEmilio Morenatti)

Protesters stand behind a banner reading in Catalan, "Freedom for Political Prisoners" at El Prat airport in Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday convicted 12 former Catalan politicians and activists for their roles in a secession bid in 2017, a ruling that immediately inflamed independence supporters in the wealthy northeastern region. (AP PhotoEmilio Morenatti)

The protesters took to the streets after nine of the 12 Catalan politicians and activists were found guilty of sedition and sentenced from nine to 13 years in prison. Four of them also were convicted of misuse of public funds. The other three were fined for disobedience. The court barred all of them from holding public office.

Police officers clash with demonstrators outside El Prat airport in Barcelona, Spain, Monday, Oct. 14, 2019. Riot police have charged at protesters outside Barcelona's airport after the Supreme Court sentenced 12 prominent Catalan separatists to lengthy prison terms for their roles in a 2017 push for the wealthy Spanish region's independence. (AP PhotoEmilio Morenatti)

Police officers clash with demonstrators outside El Prat airport in Barcelona, Spain, Monday, Oct. 14, 2019. Riot police have charged at protesters outside Barcelona's airport after the Supreme Court sentenced 12 prominent Catalan separatists to lengthy prison terms for their roles in a 2017 push for the wealthy Spanish region's independence. (AP PhotoEmilio Morenatti)

Angry demonstrators halted some trains by placing burning tires and wood on tracks, and blocking roads as well as the airport entrance.

Protesters use makeshift barricades during a demonstration at El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Protesters use makeshift barricades during a demonstration at El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Police is surrounded of smoke after protesters used a fire extinguisher during clashes at El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Police is surrounded of smoke after protesters used a fire extinguisher during clashes at El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Protesters block El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Protesters block El Prat airport, outskirts of Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday sentenced 12 prominent former Catalan politicians and activists to lengthly prison terms for their roles in a 2017 bid to gain Catalonia's independence, sparking protests across the wealthy Spanish region. (AP PhotoBernat Armangue)

Protesters stand behind a banner reading in Catalan, "Freedom for Political Prisoners" at El Prat airport in Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday convicted 12 former Catalan politicians and activists for their roles in a secession bid in 2017, a ruling that immediately inflamed independence supporters in the wealthy northeastern region. (AP PhotoEmilio Morenatti)

Protesters stand behind a banner reading in Catalan, "Freedom for Political Prisoners" at El Prat airport in Barcelona, Spain, Monday, Oct. 14, 2019. Spain's Supreme Court on Monday convicted 12 former Catalan politicians and activists for their roles in a secession bid in 2017, a ruling that immediately inflamed independence supporters in the wealthy northeastern region. (AP PhotoEmilio Morenatti)