Canadian Prime Minister Paul Martin said the United Talmud Torahs school, which was closed at the time of the blaze Monday, was firebombed.
Montreal police spokesman Yves Surprenant refused to say how the blaze started or provide details about the notes' contents, except to say they were signed by an unknown organization.
Surprenant said it was ``the most deplorable act''' he has seen in 24 years on the force.
``What was written on the notes really told us it was a hate crime,'' he said.
Quebec's French-language TVA television network reported that the notes denounced recent Israeli attacks against Palestinians, including the killing of Sheik Ahmed Yassin, founder of the Islamic Hamas movement.
Sidney Benudiz, head of the school, called the fire ``an act of terrorism, plain and simple.'' He said the school has had some graffiti and minor vandalism in the past.
Martin said the firebombing was an ``attack on freedom.''
Setting fire to ``a place of learning, where young children gather is an offense against all that Canadians cherish,'' he said.
The attack follows a recent spate of anti-Semitic violence in Toronto.
Last month, B'nai Brith Canada reported an increase in anti-Semitic incidents across the country in 2003, saying there were almost 600 cases of violence, harassment and vandalism against Jews and over 100 such incidents in Quebec alone.
At sundown Monday, Jews around the world began observances of the weeklong Passover festival, commemorating the flight of the ancient Israelites from bondage in Egypt, as described in the Old Testament.
Montreal Mayor Gerald Tremblay promised an increased police presence at Jewish institutions during the holiday period.
