Story highlights It is the farthest north the Russian spy ship has ventured

The vessel is outfitted with a variety of high-tech spying equipment

Washington (CNN) A Russian spy ship sits 30 miles off the coast of Connecticut, a US defense official told CNN, while an armed Russian warplane recently carried out a "mock attack" against a US ship.

This is the farthest north the Russian spy vessel has ever ventured, according to US defense official.

CNN reported that the Leonov, which conducted similar patrols in 2014 and 2015, was off the coast of Delaware Wednesday, but typically it only travels as far as Virginia.

The ship is based with Russia's northern fleet on the North Sea but had stopped over in Cuba before conducting its patrol along the Atlantic Coast and is expected to return there following its latest mission.

The vessel is outfitted with a variety of high-tech spying equipment and is designed to intercept signals intelligence. The official said that the US Navy is "keeping a close eye on it."

Read More