A patrol of Russian bombers flew within 40 nautical miles of Canada's northern land mass the day after Ukraine's President received a hero's welcome in Ottawa for his struggle to defend his country from Moscow's aggression. This pair of Tupolev bombers, conducting what Moscow has long referred to as training flights, are among those that have flown the closest to Canada's mainland, a government source says.

Canada scrambled CF-18s to intercept the two Russian long-range bombers at about 4:30 a.m. ET on Thursday, the source says. The Canadian planes encountered Russia's planes in the Beaufort Sea.

A similar incident Wednesday evening triggered the same response from U.S. fighter jets. NORAD told CNN that American F-22 jets were also dispatched to intercept six Russian military aircraft including Mig-31 fighters flying within 55 nautical miles of the Alaskan coastline.

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The encounters follow closely on the heels of an official visit by Ukraine's Petro Poroshenko, who has been fighting Russian-backed rebels for months and addressed Canada's Parliament on Wednesday. The Kiev leader then journeyed to Washington on Thursday where he was received warmly by U.S. President Barack Obama.

Officials in Washington believe the two incidents – Russian aircraft coming with 74 kilometres of Canada's coastline and less than 102 kilometres of Alaska – are linked to Mr. Poroshenko's trips to Canada and the United States, CNN reported Friday.

During his stop in Ottawa, Mr. Poroshenko thanked Canada for the non-lethal military aid, such as protective vests, received $200-million loans from Ottawa and served notice he would like Canada's help in obtaining satellite imagery of the Russian-Ukrainian border.

When Canada detected the bombers, it dispatched CF-18s from Inuvik, NWT, to meet the Russian aircraft, a government source says. The Canadian fighters raced to meet the bombers and once the Russian planes were intercepted and identified, they turned away from Canada's mainland.

The Tupolev bombers did not enter Canadian airspace. They did however enter Canada's Air Defence Identification Zone in the Arctic, a band of airspace north of the country's main land mass.

Similarly, in the U.S. case, the Russian planes, two Mig-31 jets, two Russian long-range bombers and two IL-78 refuelling tankers entered the U.S. Air Defence Identification Zone, but not American airspace, CNN reported.

The Russian government has previously accused Ottawa of overreacting to Moscow's training flights and making hay out of the "Russian bear in the air" for political reasons.

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Ottawa is taking a closer interest in Russian activity in the Arctic as a result of President Vladimir Putin's annexation of Crimea earlier this year.

As recently as March, however, Prime Minister Stephen Harper publicly played down any risk that conflict between the West and Russia over Ukraine could spill over into the Arctic.

It's not the only time Russian military aircraft have played cat-and-mouse with Canada in recent weeks.

On Sept. 7, three Russian planes buzzed the Canadian frigate HMCS Toronto while it was on a training exercise with Ukrainians and Americans in the Black Sea. The low-level flyovers signalled Russia was watching as tensions remain high between Moscow and Kiev.

Canadian and American fighters have intercepted about 50 Russian aircraft in the last five years.

With a report from The Canadian Press