The Russian and United States militaries both played down the significance of two Russian attack submarines patrolling in international waters off the East Coast of the U.S., although the Pentagon confirmed Wednesday that it had been years since Russian subs had extended their reach into the region.

"It is the first time … in roughly a decade that we’ve seen this kind of behavior," Defense Department Press Secretary Geoff Morrell told reporters.

The New York Times reported that a pair of nuclear-powered submarines – an Akula-class attack boat and a newer Akula-II variant – had been patrolling off the eastern seaboard in recent days.

Northern Command and the North American Aerospace Defense Command said in a statement the submarines were being monitored during transit.

Morrell made it clear the Defense Department was not worried by the incident.