At a sizable protest in the country’s west, French police have used tear gas to disperse the demonstrators.
In Sainte-Soline, thousands of people had gathered in opposition to proposals for a new water reservoir.
Once altercations started at the construction site, several police cars were set on fire.
The turmoil comes after weeks of anti-government protests over President Emmanuel Macron’s pension changes in Paris and other cities.
The most recent protest, while unrelated to those against proposals to raise the state pension age, just adds to the mounting sense of public outrage in France.
Notwithstanding a ban on rallies in the area, opponents of the irrigation project in Sainte-Soline, close to Poitiers, marched in huge numbers on Saturday.