14 February 2017, 14:57 GMT
WASHINGTON (Sputnik) — The ship, SSV-175 Viktor Leonov, remains in international waters and was detected 30 miles south of Groton Navy submarine base, according to Fox News.
The vessel, which can intercept signals and measure US sonar capability, was "loitering" in the water, according to media reports.
The United States previously detected the ship near American shores in April 2015.
