Story highlights U.S. official: Incident related to visit by Ukraine President

NORAD says six Russian aircraft flew about 55 nautical miles from Alaska coastline

Two Russian planes flew about 40 miles off Canadian coastline, NORAD says

(CNN) Two U.S. jets this week intercepted six Russian planes that neared U.S. airspace off Alaska and Canadian planes intercepted two Russian bombers that approached Canadian airspace, NORAD reported.

A U.S. official told CNN's Barbara Starr that officials in Washington think the incidents were related to the visit by Ukrainian President Petro Poroshenko, who talked to Canadian officials Wednesday and President Barack Obama on Thursday. The United States promised Ukraine $46 million in nonlethal aid for its battle with pro-Russian militants.

On Wednesday evening, two Alaskan-based F-22 fighter jets intercepted two Russian IL-78 refueling tankers, two Russian Mig-31 fighter jets and two Russian Bear long-range bombers, according to Capt. Jeff Davis of the North American Aerospace Defense Command (NORAD).

More than six hours later, early Thursday morning, two Canadian CF-18 fighter jets intercepted two Russian Bear long-range bombers in the Beaufort Sea, Davis said. Those Russian planes came within about 40 nautical miles of the Canadian coastline, he said.

Though the planes did not enter sovereign territory, the statement said, they did enter the U.S. Air Defense Identification Zone west of Alaska and the Canadian ADIZ, according to a statement.

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