Authorities in Catalonia say three people were arrested and more than 170 injured, including about 40 police officers, during clashes between protesters and baton-wielding anti-riot police at Barcelona's international airport and elsewhere across the northeastern Spanish region.

The clashes that started late Monday stemmed from an online call by Tsunami Democratic, a loose grassroots group, following the conviction of a dozen separatist leaders at the forefront of Catalonia's secession bid two years ago.

More Images
In this Monday, Oct. 14, 2019 photo, pro-independence protesters clash with police during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

Authorities in Catalonia say three people were arrested and more than 170 injured, including about 40 police officers, during clashes between protesters and baton-wielding anti-riot police at Barcelona's international airport and elsewhere across the northeastern Spanish region.

In this Monday, Oct. 14, 2019 photo, a police aims during clashes with pro-independence protesters at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

Spain's airport operator, AENA, said more than 1,000 flights were scheduled to operate normally in Barcelona Tuesday, after at least 110 were cancelled the day before.

In this Monday, Oct. 14, 2019 photo, Spanish police in action during clashes with pro-independence protesters during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police in action during clashes with pro-independence protesters during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police clash with a pro-independence protester during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police clash with a pro-independence protester during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, an injured pro-independence protesters lays on the ground during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, an injured pro-independence protesters lays on the ground during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, a Spanish police gives instructions to other police members, not pictured, during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, a Spanish police gives instructions to other police members, not pictured, during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, pro-independence protesters march towards El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, pro-independence protesters march towards El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police carry a pro-independence protesters during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police carry a pro-independence protesters during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

Interior Minister Fernando Grande-Marlaska said authorities are investigating the group.

In this Monday, Oct. 14, 2019 photo, pro-independence protesters clash with police during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, pro-independence protesters clash with police during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

Spain's airport operator, AENA, said more than 1,000 flights were scheduled to operate normally in Barcelona Tuesday, after at least 110 were cancelled the day before.

Thousands of passengers were stranded at the airport, with many forced to walk with their luggage on highways and across fields.

In this Monday, Oct. 14, 2019 photo, a police aims during clashes with pro-independence protesters at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, a police aims during clashes with pro-independence protesters at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police in action during clashes with pro-independence protesters during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police in action during clashes with pro-independence protesters during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police clash with a pro-independence protester during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police clash with a pro-independence protester during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, an injured pro-independence protesters lays on the ground during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, an injured pro-independence protesters lays on the ground during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, a Spanish police gives instructions to other police members, not pictured, during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, a Spanish police gives instructions to other police members, not pictured, during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, pro-independence protesters march towards El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, pro-independence protesters march towards El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police carry a pro-independence protesters during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)

In this Monday, Oct. 14, 2019 photo, Spanish police carry a pro-independence protesters during a demonstration at El Prat airport, outskirts of 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. (AP PhotoJoan Mateu)