Paris police say protesters angry over a labour reform damaged stores and restaurants and injured two police officers during a rogue overnight march.
Thousands of people have been gathering for the past 11 nights at the Place de la Republique to express frustration at a bill extending the workweek and making layoffs easier.
The fledgling occupy-style movement has expanded to include a range of grievances and visitors from other cities and countries.
Paris police said in a statement today that a few hundred protesters broke off overnight and blocked neighbouring streets, overturning garbage cans and smashing windows of several businesses.
It said the protesters threw projectiles at police who pushed them back.
Most of the protesters are peaceful. One group has been designated to debate a possible new constitution.
