A Russian intelligence-gathering ship has been operating off the U.S. East Coast and near the Gulf of Mexico for the past month, the Pentagon said Thursday.

"We are aware that the Russian ships Viktor Leonov and Nikolay Chiker are currently operating in waters that are beyond U.S. territorial seas but near Cuba," said Lt. Col. Tom Crosson, a Pentagon spokesman. "We respect the freedom of all nations, as reflected in international law, to operate military vessels beyond the territorial seas of other nations."

The Leonov is an intelligence gathering ship outfitted with high-tech electronic spying gear. The Chiker is an ocean-going naval tug that has been accompanying the spy ship on its mission. Pentagon officials suspect the ships were part of a spying operation since March against the U.S. nuclear missile submarine base at Kings Bay, Ga. and other U.S. military facilities.

Both ships were detected operating off the coast of Florida near the U.S. Naval Station Mayport, Fla., which is south of the Naval Submarine Base Kings Bay.

The Russian intelligence gathering coincides with heightened tensions between the United States and Russia over Moscow's recent military annexation of Ukraine's Crimea.

An official said it is possible that the electronic spying is related to watching U.S. nuclear missile submarines as part of a Russian nuclear exercise.

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