Violence broke out Sunday during a protest in northern Italy against plans for a high-speed railroad tunnel to France.

At least 200 people were injured, mostly police officers who fired tear gas at masked demonstrators who threw rocks and gasoline bombs.

Five people were arrested.

Italian President Giorgio Napolitano condemned the violence, which authorities blame on anarchists and leftists who they say infiltrated a legitimate peaceful protest.

The tunnel near the northwestern Italian city of Turin is part of a multi-billion-dollar high-speed rail line linking Milan with Paris.

Demonstrators say the tunnel wold destroy the picturesque environment of the Susa valley region.