Young people set cars on fire, broke windows and threw stones at police during a march by thousands of nationalists marking Poland's Independence Day.

Police responded with tear gas and stun grenades, while detaining around a dozen people.

Police spokesman Mariusz Sokolowski said Monday that two police officers and some other people were hospitalized with injuries they sustained during the clashes.

The nationalists marched through downtown Warsaw. Their Independence Day march has turned violent before, and Warsaw authorities, who initially allowed Monday's march, declared it illegal after the violence.

But elsewhere in the capital and other parts of the country, many Poles held peaceful events in memory of the country's regaining sovereignty in 1918 as a result of World War I.