Clashes broke out in Warsaw as riot police confronted right-wing nationalists during a Polish Independence Day march.
Some of an estimated 20,000 marchers threw fireworks and bricks at police who responded with tear gas and rubber bullets.
A police spokesman said two officers were injured and several protesters were detained.
Thousands of police had been deployed to prevent the march turning violent.
Last year, at least 200 people were arrested after clashes broke out when anti-fascist groups tried to blockade the nationalists' march.
'Extremists and hooligans'
Diverse groups including Polish patriots, nationalists and groups of football hooligans took part in Sunday's march. Many of the young men wore scarves or balaclavas over their faces.
Nationalist marches have been growing in size on the national holiday, with leftists turning out to oppose them, says the BBC's Adam Easton, in Warsaw.
Last year's march dwarfed its predecessors, with numbers swollen by football supporters outraged by a government clampdown on violent fans.
However, two other marches marking the day in 1918 when Poland regained its sovereignty after years of foreign rule passed without incident.
To prevent clashes this year the marches took different routes.
Polish President Bronislaw Komorowski also organised his own Independence Day march with military veterans in an attempt to reclaim the day from what he called "extremists and hooligans".
Ahead of the march he appealed for a less polarised society.
"Today public life is poisoned by excessive rows," he said. "We should be critical, but criticism should not mean mutual destruction."
The 11 November celebration marks the day when Poland regained its independence, 123 years after it was divided between Russia, Prussia and the Austrian Empire.