MONTREAL - Provincial police say a riot in small-town Quebec last week was the most violent protest they've seen in more than a decade and insist their response was a measured one.

Under heavy criticism for their handling of a student protest in Victoriaville, Que., that turned violent last week, provincial police say they had no choice after the event quickly turned sour.

During a news conference today, police said the event began peacefully but deteriorated rapidly after a small group of so-called "professional" rioters arrived.

Police say those hardcore protesters sparked the violence last week while police protected a Quebec Liberal Party convention, as rocks and projectiles rained down on them.

Critics have argued the police force acted far too aggressively, in a scuffle that left three people with head injuries and cost one student his eye.

But a police spokesman says the force has consulted with a pathologist who looked at the medical records of those three people. He says the opinion was that two were not injured by police rubber bullets.

Police called the riot the most violent incident they've dealt with in more than a decade, when police and protesters clashed at the Summit of the Americas in Quebec City in 2001.