Some 2,000 protesters, including a roughly 300-strong dark-clad hardcore, were in the Maurienne Valley objecting to the construction of a rail link including a tunnel between Lyon and the Italian city of Turin.
They threw rocks at riot police, who responded with tear gas, and one demonstrator was wounded, local prefect Francois Ravier told a news conference, Reuters reported.
Association Les Soulevements de la Terre contested that figure in a Twitter post late on Saturday and said 50 demonstrators were wounded, including six who were hospitalized.
"The day is not over, we remain prudent and mobilized," said Ravier, noting a security presence would go through the night.
Interior Minister Gerald Darmanin tweeted the police injury toll. Border checks turned up 400 objects, like knives and hammers, while 96 individuals known by security services were sent back to Italy, the officials said.
MP/PR