In a bulletin dated 16 December, the USCG revealed reports that the RFN Viktor Leonov (AGI-175) was neither energizing running lights nor responding to hails by commercial vessels.

The United States Coast Guard has received reports indicating that the RFN VIKTOR LEONOV (AGI-175) has been operating in an unsafe manner off the coast of South Carolina and Georgia. This unsafe operation includes not energizing running lights while in reduced visibility conditions, not responding to hails by commercial vessels attempting to coordinate safe passage and other erratic movements,

...the bulletin explained.

Vessels transiting these waters should maintain a sharp lookout and use extreme caution when navigating in proximity to this vessel. Mariners should make reports of any unsafe situations to the US Coast Guard.

Russia has boosted its military presence in east US since 2014, when it seized Crimea from Ukraine, according to CNN.

The Viktor Leonov regularly patrols in international waters along the eastern coast of the US, having done so every year since 2015.