The head of the Canadian Security Intelligence Service (CSIS) says Canadians have joined the insurgency in Iraq.

James Judd, the director of CSIS, revealed Thursday evening that some of the foreign fighters in Iraq battling coalition troops are Canadians. He said there aren't many, but more are expected to join.

Speaking to reporters at a break during a security conference in Montreal, Judd was asked if Canadians were in Iraq fighting against the American-led coalition. "Yes, I believe so," he said.

CSIS says Canadians have joined the Iraqi insurgency

He said there weren't many, "we're talking single digit numbers." But he said "we're aware of several others who are contemplating leaving."

When asked if CSIS, or the government, could do anything to prevent people from joining the insurgency Judd said he didn't think there was anything legally that could be done.

"In some instances we found out about it after the fact, and to the extent that we did have some certainty about it we would want to advise our friends and allies," said the CSIS director.

According to Keith Boag, the CBC's Ottawa bureau chief, the Prime Minister's Office was "flabbergasted" that such sensitive information could be released by the head of the spy agency. "They didn't know it was being spoken about publicly and for that they [the PMO] are very angry."

"The prime minister never comments on intelligence matters and they were under the impression that CSIS didn't either," said Boag.

Acknowledgment that Canadians are fighting in Iraq raises a number of questions, such as what will their status be if they decide to return to Canada.

"It raises the longer-term question of what do they bode for the future?" Judd said.