Hundreds of teachers in Puerto Rico have gathered with tambourines, cowbells and bullhorns outside public schools across the island as they launch a two-day strike to protest changes made to their pension plan amid an economic crisis in the U.S. territory.

Tuesday's strike coincided with the first day of classes after winter break, forcing dozens of schools to close. Puerto Rico's governor urged teachers to end the strike and meet with him.

Legislators of the main opposition party supported the strike and some parents even joined in, demanding that changes to the teachers' retirement system be revoked.

Gov. Alejandro Garcia Padilla has said the changes are needed because the system has a $10 billion deficit and will run out of money by 2020 if nothing is done.