Riot police clashed with hundreds of protesters on Thursday ahead of a NATO summit of world leaders, firing repeated rounds of tear gas and rubber bullets to try to disperse the crowds.
About 200 youths were arrested and police say they fear there could be much more violence over the next two days both in France and nearby Germany, which are co-hosting 60th anniversary celebrations for the military alliance.
More than 500 demonstrators tried to converge on the center of the French city of Strasbourg in a spontaneous protest during the afternoon, their numbers swelled by disaffected youths from the surrounding suburbs.
They smashed windows, vandalized cars and barricaded a street before being pushed back out of the city by police.
At one point, rioters charged a military vehicle that happened to cross their path, with a masked youth hurling a pole through the windshield.
One of the occupants, who was in uniform, drew his gun and pointed it toward the sky, giving the driver time to speed off.
Organizers of the anti-NATO movement, which has set up camp just outside Strasbourg, condemned the violence.