Police beat students, monks and journalists with batons as they dispersed a protest against a proposed new education law after a standoff that lasted more than a week in Burma, officially known as Myanmar.
About 100 people were detained.
Over 200 students and supporters have been protesting against an education bill they say stifles academic independence.
They had planned to walk from the central city of Mandalay to the commercial hub of Yangon, but were blocked by police in Letpadan, about 140km to the north of Yangon, earlier this month.
Police had said they would allow the students to continue their march, but that agreement fell apart.
Riot police charged at the students and their supporters, chasing some into a monastery.
Witnesses said both protesters and police used slingshots against each other.
Yangon is the site of numerous student-led demonstrations, including those in 1988 that sparked a pro-democracy movement that spread throughout the country before being suppressed by the military government.
A semi-civilian reformist government took power in 2011 after 49 years of military rule and its response to the current protests has been more muted.
A Reuters witness saw about 100 protesters locked in two police trucks after the police action, while others fled the town.
The Delegation of the European Union, which has been training the police in crowd management, condemned the crackdown and called for a formal investigation.
The British embassy in Myanmar also condemned the incident on its official Twitter feed.
Deeply concerned by use of force at Letpadan& use of irregular security groups on 5 Mar. Undermines earlier disciplined policing of protest.
— UK in Burma (@ukinburma) March 10, 2015The Interim Myanmar Press Council said it was filing a complaint, protesting "in the strongest terms against the arrest of reporters" and calling for their release, without saying how many journalists were detained.
Police and government spokesmen were not available for comment.
The Information Ministry posted photos on its Facebook page showing student protesters tearing down police barricades and noted that the protesters removed them "with force".
Student leaders rejected the suggestion that they had instigated the violence.
"It hurts my heart whenever they do this to us students, but for sure we will never use violence," said Lin Htet Naing of the All Burma Federation of Student Unions.
His wife, a former political prisoner of the previous military regime, was among those arrested in Letpadan while he led a brief protest in Yangon on Tuesday.
About 100 protesters were met in the street in Yangon by a larger number of police who grabbed one protester and beat him.
Police said they would release him if the protesters dispersed, which they did.
