A Russian spy ship has been spotted in international waters off the coast of Connecticut.

A spokeswoman for the Defense Department, Lt. Col. Valerie Henderson, said in a statement Wednesday that the Pentagon is aware of the vessel's presence.

"It has not entered U.S. territorial waters. We respect freedom of navigation exercised by all nations beyond the territorial sea of a coastal State consistent with international laws," Henderson said.

Public Affairs Specialist 1st Class LaNola Stone with the Coast Guard's First District, which covers this area, said the Coast Guard also is aware of the vessel's presence and is "monitoring it as we would any other vessel approaching the U.S."

Stone could not confirm the ship's exact location, but said by phone Wednesday afternoon that it was still off the East Coast near Connecticut.

The U.S. maritime boundary extends 12 miles from the coast, so the Cold War-era ship, the SSV-175 Viktor Leonov, which was patrolling 30 miles from the Naval Submarine Base on Wednesday, is in international waters and not doing anything illegal. U.S. ships also carry out intelligence gathering missions in international waters.

A Russian spy ship patrolling off the East Coast is not unprecedented.

"This is a ship that actually happens to visit the East Coast or at least our hemisphere with some regularity," said Michael Petersen, director of the Russia Maritime Studies Institute at the Naval War College in Newport, R.I.

It showed up in Havana, Cuba, in January 2015, and was spotted off the East Coast in April 2015, Petersen added.

The East Coast is a "target-rich environment" from an intelligence perspective, he said, given "important" naval facilities in Norfolk, Va., Kings Bay, Ga., and Groton, and the Russians have opportunities to resupply in Havana.

U.S. Rep. Joe Courtney, D-2nd District, said Kings Bay has been a more frequent destination for this type of Russian patrolling in recent years. But it's not unprecedented in the history of Connecticut, Courtney said, noting that during the Cold War it was "fairly recurrent."

Ships like the Viktor Leonov also appear quite frequently on the West Coast, where they follow around American exercises and show up in the South China Sea, Petersen said, adding that Chinese ships do the same.

The Viktor Leonov is part of the Vishnya-class of intelligence ships. A Vishnya-class ship's primary job is to collect radio and telephone signals "that it deems of value," Petersen said, but it also can carry a small complement of short-range surface-to-air missiles for defensive purposes only.

"It's not like it doesn't have teeth, but it's also not an offensive ship," he said. "There's not physical danger to anyone on the East Coast."

This type of ship usually has a crew of 145 sailors, according to Petersen, who said there are six in operation in the Russian fleet. About 300 feet long, they are almost as long as a football field and displace about 3,500 tons. A U.S. Arleigh Burke-class destroyer displaces about 10,000 tons, and is just over 500 feet long.

While Russian ships patrolling near the U.S. coast is nothing new, given recent events such as National Security Adviser Michael Flynn's resignation and reports of Russia violating a decades-old arms treaty, "there's a little more sensitivity to this," Petersen said.

Flynn resigned Monday, apologizing in his resignation letter for giving "incomplete information" to Vice President Mike Pence and other White House officials about his calls with Russia's ambassador to the U.S. On Tuesday, a Trump administration official said that Russia had deployed a cruise missile, violating the 1987 Intermediate-Range Nuclear Forces Treaty.

The spy ship's patrolling and Russia's buzzing of a U.S. Navy destroyer in the Black Sea last week, which was confirmed by officials Tuesday, are incidents that "are clearly testing the resolve of a new administration," Courtney said in a statement.

He called the move by the Russian ship an "unacceptable, aggressive action."

"A Russian spy ship patrolling 30 miles from the Groton SUBASE underscores that the threats posed by a resurgent Russia are real," said Courtney, ranking member of the House Seapower and Projection Forces Subcommittee.

Courtney said by phone Wednesday morning that he'd been in touch with Capt. Paul Whitescarver, commanding officer of the sub base, who is "very confident that there is a battle plan to monitor this." Navy officials in the Washington, D.C., area, Courtney said, are monitoring the situation "like a hawk."

"While I have total confidence in our Navy's vigilant, responsible readiness, the White House needs to move past their seeming infatuation with Putin and treat him like the serious threat to global peace and security that he has been for the last five years," Courtney said.

U.S. Sen. Chris Murphy, D-Conn., also put out a statement Wednesday morning responding to reports of the ship, saying that while not "wholly unprecedented, it's part of a series of aggressive actions by Russia that threaten U.S. national security and the security of our allies."

Murphy, ranking member of the Senate Foreign Relations Subcommittee on Europe and Regional Security Cooperation, also pointed to Russia's buzzing of the Navy destroyer.

"Coupled with escalating fighting in eastern Ukraine and Russian jets buzzing a U.S. Navy destroyer in the Black Sea, Putin clearly thinks the Trump administration has given him a permission slip to flex his muscles. President Trump and his administration must end their silence and immediately respond to these threats to our national security," Murphy said.

j.bergman@theday.com