SANTIAGO, Chile (AP) --— Police have used water canons and tear gas to break up a protest in Chile's capital by thousands of students demanding free education.

Small groups of hooded vandals often mingle in student protests, setting ablaze traffic lights and hauling rocks at police and three buses were set ablaze in yesterday's demonstration.

Presidential spokesman Andres Chadwick says student leaders cannot be exempt from responsibility after the burning of the Transantiago mass transit system buses.

Santiago's municipal government had banned the students from flooding the streets of the capital, fearing the protest would turn violent. Demonstrations demanding education reforms have swept Chile for more than a year. The government says the latest one in late June turned out to be the most violent with 472 demonstrators arrested and 36 police officers injured.