Russian aircraft on Friday reportedly flew near Alaska for the fourth time in four days.

Two TU-95 “Bear” long-range bombers flew within the U.S. Air Defense Identification Zone (ADIZ) about 700 nautical miles southwest of Anchorage, though they remained in international airspace, CNN reported. It was not clear if the U.S. scrambled jets to intercept the aircraft.

While such flights are not out of the ordinary, the episode signals a major uptick in the frequency at which Russian aircraft are flying near the U.S.

ADVERTISEMENT

Similar flights in past days have been intercepted by U.S. jets and escorted out of the ADIZ. The flights mark the first time since 2015 that Russian planes have approached the U.S. mainland.

The Russian Defense Ministry said in a statement obtained by CNN that the flights have been conducted with regard to international regulations and have not violated U.S. airspace.

"All such missions are carried out in strict compliance with international regulations and with respect to national borders," the statement reads.