Hundreds of demonstrators assaulted the construction site of the Turin-Lyon high-speed rail line at Chiomonte, in Val di Susa, during a march organized by the No Tav movement. Four police vehicles, two belonging to the Carabinieri and two to the Guardia di Finanza, were set on fire. Approximately 60 officers were injured.

The demonstrators, dressed in black and wearing helmets and gas masks, threw stones, bottles, paper bombs, and rockets, including homemade mortars, at the officers deployed to protect the site. Law enforcement responded with tear gas and water cannons from inside the construction site. The clashes lasted over an hour, after which the demonstrators retreated into the woods.

The march, described by its organizers as heading "toward the construction sites of devastation," departed from Venaus in the early afternoon. According to the organizers, approximately 20,000 people participated. Tensions were also reported at the San Didero construction site, where officers launched tear gas to push back demonstrators, with clashes lasting about twenty minutes.

For security reasons, traffic was suspended on the A32 highway between Oulx and Susa Est, and rail service was halted between Bussoleno and Borgone Susa due to the presence of demonstrators on the tracks. Before the demonstration, law enforcement seized slingshots, rockets, marbles, firecrackers, and fireworks at Bardonecchia station. The prefect of Turin had imposed restrictions and bans, while the police chief issued fourteen measures including urban Daspo orders and removal notices. Some French citizens were subjected to removal from Italian territory for public order reasons.

Political reactions were unanimous in condemning the violence. President of the Republic Sergio Mattarella called Interior Minister Matteo Piantedosi to express solidarity and closeness to the injured officers. Prime Minister Giorgia Meloni stated that those who assault law enforcement are attacking the State. Minister Piantedosi spoke of an escalation requiring maximum attention and called for a united stance from all political forces and institutions.

The opposition condemned the clashes with some distinctions. The Five Star Movement expressed closeness to the injured officers and condemned acts of violence, adding that the clashes divert attention from the project's costs, indicated at 14.7 billion euros with a 127% increase over initial estimates according to the European Court of Auditors. The mayor of Turin, Stefano Lo Russo of the Democratic Party, condemned the damage while reaffirming the right to express dissent as a fundamental value of democracy. Angelo Bonelli of the Greens and Left Alliance stated that defending the territory is achieved through democratic mobilization and nonviolence, and that those who use violence harm everyone.

Foreign Minister Antonio Tajani called the left "complicit," while Deputy Prime Minister Matteo Salvini spoke of "poisonous fruits of a left" that fuels hatred against law enforcement. These assessments were rejected by opposition forces, which reiterated their condemnation of violence.