Officers swarmed the site at Notre-Dame-des-Landes before dawn to evict around 100 of the protesters who had occupied it to prevent the construction of a controversial airport and then refused to leave after the project was ditched.
The police fired tear gas to disperse the protesters, who hurled petrol bombs at the security forces and tried to block their advance with burning barricades of tyres and wooden pallets.
One officer was injured in the eye, the interior ministry said, while security sources said one person was arrested.
In January, the government scrapped the decades-old plans for a new airport to serve the Atlantic coast and told the protesters to clear out by spring.
But some of the motley group of eco-warriors, farmers and anti-capitalists, who had turned the area into a utopian experiment in autonomous living, had demanded the right to stay put.
In a statement, the protesters expressed anger over the destruction of their huts and shelters, vowing that “We will not leave”.
The activists moved onto the site in 2008 and have since built up a community that they bill as a model of sustainable farming and political debate.
A first attempt to evacuate them in 2012 failed.
In January, President Emmanuel Macron buried plans for the airport, ending years of dithering by successive governments.
Supporters had argued that it would boost the local economy but environmentalists countered that the area had unique flora and fauna and that a new facility costing 730 million euros ($890 million) was unnecessary given relatively light traffic at the existing Nantes airport.
aag-alh-asl-grd/cb/js
Download our app and read this and other great stories on the move. Available for Android and iOS.