Chilean authorities arrested 75 people after police used tear gas and water cannons to crack down on student protesters in the capital who torched three city buses, injuring 49 police, the mayor's office said.
Transport Ministry officials said hooded protestors forced people off the buses before they set them ablaze.
"This is unacceptable," Transport Minister Pedro Pablo Errazuriz said in televised remarks. "I have trouble understanding what kind of people would cause this type of damage."
Government spokesman Andres Chadwick voiced his dismay as well.
"Student leaders who call these illegal, unauthorized marches (with no permits), know perfectly well they are opening the door to vandalism and crime," he said.
Students have staged scores of marches in the city to press demands for major reforms including free university education and improvements in the quality of higher education here.