Two pairs of Russian Tupolev Tu-95 bombers approached the U.S. West Coast on Saturday, forcing the Air Force to scramble fighter jets to intercept the war planes before they breached the U.S. airspace, Fox News reported Monday. The Russian bombers were capable of carrying nuclear weapons, but North American Aerospace Defense Command (NORAD), which identified the planes, did not indicate whether they were armed.

The first pair of Tupolev Tu-95 bombers was detected at 10:30 a.m. EDT off the coast of Alaska when NORAD scrambled two F-22 jets to intercept the Russian long-range strategic bombers. The second incident occurred at 11:00 a.m. EDT off the central coast of California, and two F-15 jets were scrambled from an undisclosed location, Fox News reported, citing two senior U.S. defense officials.

“These are not unprecedented flights, but we are postured to respond whether Alaska or California,” Michael Kucharek, a spokesman for NORAD, told Fox News. “At no time did the bombers enter North American sovereign airspace.”

Although the Russian bombers did not breach the U.S. airspace, the presence of the planes off the West Coast is deemed threatening amid increasing tensions between Moscow and Washington.

“It’s becoming very obvious that Putin is testing [Barack] Obama and his national security team,” retired Air Force Lt. Gen. Thomas McInerney, a former Alaska commander for NORAD, told the Washington Free Beacon. “These long-range aviation excursions are duplicating exercises I experienced during the height of the Cold War when I commanded the Alaska NORAD region.”

Meanwhile, Sputnik News reported, citing the Russian Ministry of Defense, that all flights conducted by the country’s air force are routine, and in compliance with international agreements.

On Saturday, two Russian bombers were also reportedly spotted east of the big Swedish island of Gotland. The Swedish Armed Forces, which subsequently scrambled two fighter jets to monitor the bombers’ activities, said that the planes did not violate Swedish airspace.