U.S. stealth fighters were scrambled again Thursday night to intercept Russian long-range bombers near the Alaska coast as such encounters this week reached the highest level in years.

The Russian TU-95 "Bear" bombers were spotted in international airspace around 7 p.m. and met by two F-22 fighters jets and two Canadian CF-18 Hornet fighters, according to U.S. Northern Command. The command declined to say how close the aircraft came.

Moscow sent aircraft into the area every day this week, though none penetrated U.S. territory. The incidents represent the biggest uptick in Russian activity there in since 2014, said Lori O'Donley, a spokeswoman for the command.

"This isn't anything unprecedented" and the Russian aircraft acted professionally and appropriately, she said.

Since about 2007, the United States has intercepted Russian aircraft about 60 times. Some years have seen up to 15 incidents while other years have none, O'Donley said.

But the increased Russian presence near Alaska this week has taken on added significance because it comes amid rising tensions over Moscow's support of the Assad regime in Syria, aggression toward Europe and meddling in the U.S. presidential election.

Secretary of State Rex Tillerson said relations between the two countries are at a historic low point during a visit to Russia earlier this month.

On Wednesday, a Russian Il-38 maritime patrol aircraft flew near Alaska and was identified by the United States but was not intercepted by fighters, O'Donley said.

The incidents on Tuesday and Monday involved the nuclear-capable Russian bombers and the scrambling of the U.S. fighter jets, she said.