Around 10 or 12 militants wrenched open several distillation tanks at a plant north of Montpellier, causing €500,000 worth of damage and pumping almost 400,000 litres of Chilean and Argentinean wine into the nearby river.
The initials of the Comité Régional d'Action Viticole, Languedoc Rousillon's militant vintner group, were spray-painted on the distillery's walls and tanks.
The attack is the latest in a string of assaults that have revealed the vulnerability of foreign wine in southern France and the security problems now faced by importers and distributors.
The latest CRAV action happened just hours after between eight and eleven thousand local wine makers staged a peaceful yet highly emotional protest in Nimes.
Protestors marched through the streets with hooters, fire crackers, long-arm steel hammers and flare guns to complain at a lack of government help to alleviate the severe pressure on many wine businesses.
The problems of falling domestic consumption, rising production and shrinking export markets have bubbled over into a veritable crisis in recent months.
The government has offered €140m to help the industry, but many wine makers at Nimes were livid at the red tape surrounding the industry and a lack of government direction.
"The price of wine is going down and down everywhere, but France cannot compete with other countries at the moment because of the costs for French wine makers," said M. Montagneux who works in the wine trade.
Pierre Clavel is an established 'appellation contrôlée' wine maker in Languedoc and has so far avoided the worst of the trouble, yet even he was angry with government rules shackling the industry.
"I know wine makers in Spain and they are laughing at us, just laughing. We are expected to spend our time doing paperwork, while they can put all their energy into producing good wines," he said.
Jean Huillet, president of the union of wine cooperatives in Herault, told crowds at Nimes that the government had lost all credibility with agricultural workers. He and many others actively campaigned for a French 'no' vote to the EU constitution.
"Our wines are going nowhere. Prices are falling and we are losing contracts," said Philippe Vergnes, union president in the neighbouring Aude region.
Agnes Payan, an independent vintner from the Cotes du Rhône region, said retailers and restaurants had also taken advantage of the production surplus. "I was getting between €2 and €3 for my wines last year but now it is around €1."
A couple of hard discounter stores, an Aldi and a Lidl, were trashed as vintners made their way home from the Nimes protest.
Two wine makers from Aude were arrested but later released after Vergnes intervened to negotiate with police.
No more large-scale protests are planned, but the anger among many French vintners has shown no sign of diminishing in recent weeks.