Jim Judd, who leads the Canadian Security Intelligence Service told the Toronto Star that a new generation was honing terror skills in Iraq and voiced concern the violence could surge in their home countries.
"We all obviously hope the conflict in Iraq ends soon, but then worry about what all these people are going to do," he said.
"They will re-migrate around the world and return home. At the end of the day a lot of the issues that motivate these people are so varied and different that they will carry on possibly beyond their service in Iraq and continue to be motivators, what are now well-trained, highly effective, dangerous people," said Judd.
Judd said there are Canadian citizens in Iraq and others that "we know are planning to go," while declining to offer further details.
Asked about Canadians' widespread perception that their country is not a priority for terrorists Judd said he hoped to change that impression.
"We're not scaremongers," he said. "We are responsible in what we do; but there are people who pose threats to the country."