There were clashes between rival groups in the Polish capital, Warsaw, on Independence Day on Friday.
About 20 people were taken to hospital with injuries and more than 150 were arrested.
The BBC reports marches by nationalists have been growing in size on the national holiday, opposed by left-wing activists.
Police used water cannon and pepper spray to bring the situation under control.
11 November marks the day in 1918 when Poland regained its independence, 123 years after it was divided between Russia, Prussia and the Austrian empire.
