Washington ( CNN ) -- Russian bomber aircraft were spotted last week off Alaska and then within 50 miles of California , military officials said . Four long-range planes flew close to Alaska on June 4 where they were intercepted by U.S. F-22 fighter jets . Two peeled off and headed west , while the other two flew south and were identified by American F-15 fighters within 50 miles of the California coast . Details were confirmed to CNN on Thursday by the Defense Department and the North American Aerospace Defense Command , a joint U.S.-Canadian force . The United States believes the Russians were on a training mission , Pentagon spokesman Col. Steve Warren said . The planes , which included Tu-95 Bear-H bombers and refueling aircraft , never breached U.S. air space , Capt . Jeff Davis , a NORAD spokesman , said . But they did enter the U.S. Air Defense Identification Zone , which is an area extending 200 miles from the North American coast and is mainly within international airspace . Commercial and other planes must identify themselves when they fly through that zone . `` They followed all the protocols and it was a very professional encounter on both sides , '' Davis said . `` There was nothing that they were doing that was contrary to international law . '' NORAD intercepts Russian bombers in the defense zone about 10 times a year , Davis said , though usually not near California . Russian military planes were last intercepted off the coast of California on July 4 , 2012 , Davis added . Ukrainian official : Russian tanks have entered the country . CNN 's Barbara Starr , Jeremy Diamond , and Joshua Berlinger contributed to this report .
Military officials say two bombers and a refueling plane involved . They first flew near U.S. and then two were seen within 200 miles of U.S. . The planes never entered U.S. airspace , but did breach a coastal identification zone . The Russian planes were intercepted by U.S. fighter jets .