Mariners told to use 'extreme caution' after Russian spy ship spotted off East Coast

Mariners were told to use "extreme caution" after a Russian spy ship was spotted off the southeast coast of the United States this week "operating in an unsafe manner," according to the Coast Guard.

The Russian surveillance ship, named the Viktor Leonov, is now hundreds of miles off the Florida coast and east of the Bahamas after moving in a southerly direction for the last several days, a U.S. defense official told ABC News.

In a bulletin posted Tuesday morning, Coast Guard Sector Jacksonville warned that the Russian spy ship was operating in an "unsafe manner," including "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."

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

Coast Guard offices in South Carolina and Georgia also issued similar warnings in the last several days.

In a statement to ABC News, a spokesperson for North American Aerospace Defense Command (NORAAD) and United States Northern Command (NORTHCOM) said they "closely track vessels of interest, including foreign military naval vessels such as the Russian ship Victor Leonov, in our area of responsibility."

"We are aware of Russia's naval activities, including the deployment of these intelligence collection ships in the region," the statement said. "While we won't discuss specific measures being taken, NORAD and USNORTHCOM routinely conduct air and maritime operations to ensure the defense of the United States and Canada."

A U.S. Navy destroyer, the USS Mahan, is shadowing the Russian ship, a second defense official said.

The Leonov, which typically carries electronic surveillance equipment and some weapons for self-defense, is no stranger to the eastern seaboard, having made similar treks in years past.

It made headlines in 2017 after being spotted off the coast of a U.S. Navy submarine base in Connecticut in February before making its way south. Then in March, the Leonov was seen near the submarine base at Kings Bay, Georgia following a five-day port visit in Havana, Cuba.

During that 2017 visit, the ship remained in international waters beyond the U.S. territorial limit that extends 12 miles out from shore, and U.S. officials downplayed its presence off the coast, noting the ship had made prior visits in years past.