The Pentagon is unconcerned by the presence of two Russian submarines in international waters off the U.S. coast, the Pentagon press secretary said at a news conference.

Geoff Morrell told journalists on Wednesday, "So long as they are operating in international waters - as, frankly, we do around the world - and are behaving in a responsible way, they are certainly free to do so and it doesn''t cause any alarm within this building."

The New York Times reported late on Tuesday that the two submarines had been in the area for several days. The newspaper quoted defense department officials as saying one of the Akula-class vessels remained 320 kilometers (200 miles) off the coast, while the location of the second was not clear.

Despite the Russian Navy increased activity in recent years on the world''s oceans and participation in foreign exercises, including Venezuela last December, Morrell said the latest report was not unusual and admitted that U.S. submarines also operate off the Russian coast "from time to time."

"While it is interesting and noteworthy that they are in this part of the world, it doesn''t pose any threat and it doesn''t cause any concern," Morrell said.