The U.S. Navy spotted a Russian nuclear attack submarine sailing in international waters about 440 kilometers off the southeastern U.S. coast two weeks ago and has been tracking it ever since, CNN reported, citing U.S. defense officials.
The Sierra-2 Kondor class submarine, which is believed to belong to the Northern Fleet, has not entered U.S. waters as it apparently conducted Cold War-style anti-submarine exercises, the report said.
U.S. defense officials, who spoke to CNN on condition of anonymity, citing the sensitivity of the issue, refused to say how the submarine had been detected. "Things worked the way they were supposed to," one official was quoting as saying.
The submarine has now turned toward Europe and was located about 950 kilometers off the U.S. coast on Tuesday, officials said.
The submarine spotting was first reported by the Washington Free Beacon, which also reported in August that a Russian nuclear submarine had traveled undetected for up to a month in the Gulf of Mexico. The Pentagon denied that report.
Defense officials told CNN that the U.S. previously detected a Russian submarine close to its shores in 2009.