NORAD is downplaying an incident on Tuesday that saw two CF-18s shadow a pair of Russian military aircraft as they flew within 56 kilometres of Canadian soil.

Two CF-18s, similar to this one, shadowed a pair of Russian military aircraft Tuesday north of Inuvik, N.W.T. The encounter came a day before parliamentarians were to discuss the government's purchase of F-35 Joint Strike Fighters, slated to replace Canada's CF-18s.

In a statement Wednesday, NORAD, the North American Aerospace Defence Command, said the CF-18s "intercepted and visually identified" two TU-95 Bear bombers that entered the Canadian Air Defence Identification Zone.

"At no time did the Russian military aircraft enter Canadian or United States sovereign airspace," said NORAD spokesman Lt. Desmond James, a Canadian naval officer.

"Both Russia and NORAD routinely exercise their capability to operate in the North. These exercises are important to both NORAD and Russia and are not cause for alarm."

In a "readout" email to media early Wednesday, PMO communications director Dimitri Soudas said the aircraft were spotted approximately 220 kilometres north of Inuvik, N.W.T.

The CF-18 jets from 4 Wing Cold Lake in Alberta shadowed the Russians until both aircraft turned around, Soudas said.

"Thanks to the rapid response of the Canadian Forces, at no time did the Russian aircraft enter sovereign Canadian airspace," he said.

The Canadian aircraft returned to base without incident.

NORAD said its aircraft have intercepted four Russian bombers so far this year and 16 times in 2009.

James said NORAD recognizes that all countries have the right to operate in international airspace, but may conduct identification missions should aircraft approach the North American Air Defence Identification Zone.

Soudas said Prime Minister Stephen Harper, who is in the Canadian North for his annual Arctic tour, was briefed during and at the end of the mission.

A spokesman for the Russian Embassy in Ottawa noted that Canadian authorities repeatedly confirmed the Russian bombers never entered Canadian airspace.

Spokesman Sergey Khudyakov said Russia respects Canada's "territorial integrity, including the vast Arctic territories under the Canadian sovereignty."

"All flights are being conducted within the international airspace with solely training purposes," Khudyakov wrote in an email to CBC News on Wednesday.

Defence committee to probe F-35 purchase

News of the encounter comes ahead of the House of Commons defence committee's meetings on Wednesday to examine the government's single-bid purchase of the new generation of F-35 Joint Strike Fighters.

Soudas's email touted the "new, highly capable and technologically advanced" F-35s, which are slated to replace Canada's CF-18s sometime in the next decade.

"It is the best plane our government could provide our Forces, and when you are a pilot staring down Russian long-range bombers, that's an important fact to remember," Soudas said.

The contract, one of the biggest military equipment purchases in Canadian history, is worth $9 billion, but the full cost could rise to as much $18 billion once the government signs a maintenance contract.

The Liberals want the committee to question other potential bidders and procurement experts to determine whether a sole-sourced contract gives maximum value to the government and taxpayers.

Last week, the prime minister declared the protection and promotion of Canada's sovereignty in the Arctic a "non-negotiable priority."

'Diversion' from criticism

Liberal MP Larry Bagnell said he did not know the full details surrounding the latest incident, but suggested the Conservatives had used a previous CF-18 encounter with Russian planes in July as a "diversion" from criticism of the F-35 purchase.

Bagnell told reporters in Ottawa on Wednesday that the government was "needlessly" creating a foreign relations issue with Russia just days after saying that working with other countries to resolve Arctic border disputes was Canada's top foreign affairs priority.

"How are we going to work with a country we've just chastised for not even coming into our airspace?" Bagnell said.

NDP defence critic Jack Harris dismissed the government's interpretation of the encounter, saying there's not been any incursion into Canadian airspace in decades.

Russia, Harris said, resumed these flights a couple of years ago "just to prove they could get their planes in the air."

"But there's certainly no threat to our sovereignty," he added.

'Nothing else will do it'

But Conservative MPs said the interceptions show that Canada must exercise its Arctic sovereignty by being present in the North, including militarily.

"The only way we can be in the North rapidly to counter someone who is also trying to exercise sovereignty is with an airplane like the F-35," said Tory MP Laurie Hawn, a retired RCAF lieutenant-colonel who serves as parliamentary secretary to Defence Minister Peter MacKay.

"Nothing else will do it."

NORAD is a binational military organization established in 1958 by Canada and the U.S. to monitor and defend North American airspace.

Earlier this month, military personnel from Canada, the United States and Russia teamed up for the first time to test their response to a hijacked commercial jet over North American airspace.