Syed Soharwardy, founder of the Islamic Supreme Council of Canada (ISCC), called on Canadian and Western authorities to intensify the fight against jihadist movements.
"Absolutely I am convinced that this recruitment is going on right here in this country, under our noses, in our universities, in our colleges, in the places of worship, in our community," he told CBC public television.
Soharwardy added that a Muslim man from Ottawa who was fighting with IS in Mosul in northern Iraq had sent him a death threat on Facebook.
The Calgary-based imam said such threats were nothing new.
"I get death threats from everybody," he said, adding that "just last month I had a death threat posted on a website."
In February, intelligence services said at least 130 Canadians were fighting with IS in Iraq and Syria.