Some 70 protesters were lobbing projectiles at police from behind barricades set up to defend the camp at Notre-Dames-des-Landes near the city of Nantes, met with volleys of tear gas and rubber grenades.
Activists opposed to plans to build an airport first began squatting on the farmland in 2008 and it had since grown into a sprawling 1,600-hectare (4,000-acre) settlement billed as a utopian leftist farming community.
But the government announced in January that it was calling off plans for the airport and warned the squatters that they must clear off the land by spring.
The three days of running battles between some 2,500 police officers and the protesters -- armed with molotov cocktails and even tennis rackets to return the tear gas cannisters -- are a re-run of a failed attempt to clear the camp in 2012.
The activists have called on supporters from further afield to come and defend the camp, furious at police damage to their shelters and farming projects including a sheep shed and cheese-making area.
"We are outraged, what else could we be," said a protester who gave her name as Sarah.
"We have done everything to try to build a dialogue and they've opted for violence and destruction."
The government had said activists could stay on the land if they came up with individual farming schemes but most refused, saying they want to run the site collectively and be able to pursue non-agricultural projects.
The protesters say around 30 activists have been injured in the clashes, two of them hospitalised.
On the police side, 14 have been hurt, according to the interior ministry -- four of them suffering breathing problems after a tear gas cannister went off by accident.
Local authorities say 16 of the encampments dotting the farmland were cleared in the first two days of the operation, 15 of them demolished.
The plan is to dismantle up to 40 as authorities seek to retake control of a key road running through the area that has been blocked for five years.