The statement follows the capture last December of an Algerian-born man, Ahmed Ressam, as he tried to cross into the United States from Canada while allegedly carrying bomb-making equipment.
In its annual report, the Canadian Security Intelligence Service (CSIS) said the arrest of Mr Ressam and a number of associates was an indication that extremists had intensified their activities in North America.
The report says that, while state-sponsored terrorism continued to pose a significant threat, "one of the prime motivators of terrorism today is Islamic religious extremism."
"In the past few years, Sunni Islamic extremism, exemplified by terrorist financier Osama bin Laden, has emerged as the pre-eminent international terrorist threat."
'The financier'
Last month, President Clinton accused Mr bin Laden of financing Mr Ressam - a charge denied by his lawyer.
The US has demanded that Afghanistan extradites Mr bin Laden to stand trial on charges of masterminding the August 1998 bombings of US embassies in Kenya and Tanzania, which killed more than 200 people.
CSIS said Canada's open society and proximity to the United States meant the country was becoming an increasingly attractive base for foreign terrorists.
The Intelligence Service also said it was concerned that extremists were trying to manipulate immigrant communities in Canada.
"Despite warnings by the Canadian government that it is deemed unacceptable, certain governments consider it in their best interest to monitor the activities of political opponents living in Canada and coerce expatriate nationals," the report said.
'Friendly' threat
CSIS acknowledges that Canada is also threatened by its own allies.
"Foreign governments, including some of Canada's allies and trading partners, direct their departments, state-owned corporations and intelligence services to engage in economic espionage against Canada," CSIS said.
The most sensitive areas of economy include aerospace, biotechnology, communications, information technology, nuclear energy, oil and gas, the report says.
CSIS is also concerned that other countries have targeted Canadian trade negotiations, military and technological development, and classified Nato exchanges.
Another serious problem is the smuggling of illegal immigrants - mainly from China - and the powerful financial resources enjoyed by crime groups from Eastern Europe and Asia.
"Several groups have an increasing presence in Canada and its economy through Canadian nationals and companies used to launder hundreds of millions of dollars," the CSIS reports says.