MADRID (AP) — 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.

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

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.