It started peacefully but ended with truncheons and tear gas as police and protesters clashed in the Italian Alps.
Tens of thousands of people gathered in the Susa valley near Turin to show their opposition to the building of a high-speed railway line linking Italy and France.
Things turned ugly after security forces cordoned off a road and some demonstrators tried to push through. At least two policemen and one protester were reported injured. Thursday’s rally – the third in consecutive days – has heightened concern that anger over the project could mar the 2006 Winter Olympics being hosted by Turin.
The rail line will more than halve the journey time between the city and Lyon in southeastern France.
However controversy centres on a tunnel more than 50 kilometres long that is scheduled to be built through the Alps.
Opponents claim the work will damage the environment and could release toxic asbestos in the mountains.