Harper, who was in the Northwest Territories town of Fort Smith to announce initiatives to promote fresh food production in the region, said Russia has not made the same sort of aggressive military incursions in the Arctic as it has in Eastern Europe.
But the prime minister gave a "cautious yes" when asked if he was concerned about the militarization of the Arctic.
"Cautious in the following sense: that we haven't seen, obviously, the kind of aggressive moves in the Arctic that we have seen in eastern Europe by the Russians," Harper said.
"In fact, we have actually seen the Russian government ... actually operating within international rules.
"However, I don't think — because of what's happening elsewhere and because of what's happened for many years now — we should be complacent about this."
Russia is busy rebuilding former Soviet-era military bases in its north, and has a fleet of nuclear-powered submarines and icebreakers patrolling its waters. Russian planes have also tested the boundaries of Canadian airspace, Harper said.
"I just think we should not be complacent, because we have seen over the period that President Putin has been in power just a gradual growing in aggressiveness of his government toward neighbours and the gradual military assertiveness of that country, and I just think it's something we should never be too at ease about," he said.
In the coming days, the prime minister will take part in a series of military manoeuvres in the Northwest Passage meant to assert Canada's Arctic sovereignty.
Harper also called on Russia to withdraw a convoy of trucks that crossed across its border into Ukraine in what Moscow said was part of a humanitarian mission but which the Ukrainians called a "direct invasion."
"Look, it's disgraceful," the prime minister said.
"It's not surprising, but it is disgraceful that this latest military incursion would be under the guise of humanitarian assistance."
The incursion drew condemnation from the United States and NATO, which said Friday is has a growing body of evidence to suggest that Russian soldiers are operating within Ukraine and launching artillery attacks from within the country.
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