The police action is reported to have taken place at 3.30am Wednesday near the village of Venaus where a preliminary worksite has been set up for the construction in the Susa Valley of a rail line and 53km tunnel under the western Alps.
Local medical sources said none of the injuries appeared to be serious but the situation remains tense in the area with protestors occupying key roads and rail links in the valley.
Leaders of the protest have accused police of using undue violence and called for a general strike in the region.
The Susa Valley link will be part of a railway line connecting Turin to the French city of Lyon and ultimately part of a pan-European transport system to connect Western and Eastern Europe with a freight line stretching from Kiev in Ukraine to Barcelona in Spain.
Work on the 15.2-billion-euro link had been due to start on last Wednesday with work on an exploratory 10km narrow tunnel near Venaus.
But up to 20,000 protesters gathered on the streets of Venaus and set up barricades to prevent construction vehicles and equipment passing.
Hundreds of other demonstrators continued a non-stop vigil at the tunnel site to prevent the work starting.
The demonstrators, who have staged repeated protests against the project, say that drilling through the mountains to create the rail tunnel will create an environmental disaster and ruin the Susa Valley.
They stress that the tunnel will take at least ten years to complete and argue that the money would be better spent on boosting existing transport infrastructure in the region.
They also say they fear for their health given that the mountains contain both uranium and asbestos which might have to be excavated.
Supporters of the project, including the European Commission, say the line will cut pollution by reducing the amount of goods transported by road.
Last week, President Carlo Azeglio Ciampi renewed his support for the project saying that "Italy cannot allow itself to be cut off from the great European transport networks. We must use technological progress and scientific knowledge to guarantee the protection of the environment".
Ciampi joined the battle to modify the original project, which initially would have bypassed Italy by cutting through an area to the north of the Alps.
The company Lyon Turin Ferroviare (LTF) has already began work on the French side of the tunnel, which is due to be completed by 2015.