Russian spy ship spotted 'operating in an unsafe manner' off southeastern US: Coast Guard

JACKSONVILLE, Fla. -- The Coast Guard issued a warning to mariners after receiving reports that a Russian ship had been operating unsafely off the Eastern Seaboard.

"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," Coast Guard Sector Jacksonville said.

Other vessels in the area should "maintain a sharp lookout and use extreme caution when navigating in proximity to this vessel," the Coast Guard warned.

The ship 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.

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

The Russian spy ship was spotted off the coast of a U.S. Navy submarine base in Connecticut in February 2017 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 the its presence off the coast, noting the ship had made prior visits in 2012, 2014 and 2015.

ABC News contributed to this report.