WASHINGTON (AP) — U.S. fighter planes intercepted two Russian bombers flying unusually close to an American aircraft carrier in the western Pacific during the weekend, The Associated Press has learned.

A U.S. military official says that one Russian Tupolev 95 buzzed the aircraft carrier USS Nimitz twice, at a low altitude of about 2,000 feet, while another bomber circled about 50 nautical miles out. The official was speaking on condition of anonymity because the reports on the flights were classified as secret.

The Saturday incident, which never escalated beyond the flyover, comes amid heightened tensions between the United States and Russia over U.S. plans for a missile defense system based in Poland and the Czech Republic.

Such Russian bomber flights were common during the Cold War, but have been rare since.