The submarine was identified by its NATO designation as a Russian Seirra-2 class submarine believed to be based with Russia’s Northern Fleet. It was the first time that class of Russian submarine had been detected near a U.S. coast, said officials who spoke on condition of anonymity because of the sensitive nature of anti-submarine warfare efforts.

One defense official said the submarine was believed to have been conducting anti-submarine warfare efforts against U.S. ballistic and cruise missile submarines based at Kings Bay, Georgia.

A second official said the submarine did not sail close to Kings Bay and also did not threaten a U.S. aircraft carrier strike group that was conducting exercises in the eastern Atlantic.