Moscow accused the United States of hysteria today after reports that Russian nuclear submarines were patrolling off the East Coast of America.

Russian officials responded vehemently to accusations that they were dabbling in Cold War-style cat-and-mouse manoeuvring but did not deny that two vessels had entered international waters just 200 miles of the US coast.

“Activities of Russian submarines in the world’s oceans outside their own waters do not violate international maritime law and are within normal practice,” a military-diplomatic source told the Russian state media.

US defence and intelligence officials told the New York Times that two Akula class nuclear-powered submarines had approached the US a few days after Vladmir Putin was photographed testing a Russian submarine during his holiday in Siberia.

The Russian military source said that Moscow would not comment on the location of its fleet and suggested that the US should also refrain from discussing their whereabouts.

“The Russian navy systematically pinpoints the location of NATO submarines, including US Navy submarines, in direct proximity to the territorial waters of the Russian Federation," the official said.

“This however has never been a reason to make a lot of noise in the press... consequently, any hysteria in such a case is inappropriate."

US officials claimed that the Pentagon is concerned by the first such military move in more than a decade.

The episode does not appear to pose any immediate threat to the United States, but it echoes the Soviet and US military tit-for-tat measures taken during the Cold War when Moscow and Washington routinely sent submarines towards one another’s coasts to gather intelligence and track fleet movements.

A senior US Defence Department official said: “Any time the Russian Navy does something so out of the ordinary it is cause for worry.

“We’ve known where they were and we’re not concerned about our ability to track the subs,” said the official. “We’re concerned just because they are there."

Norman Polmar, a naval historian and submarine warfare expert, said: “I don’t think they’ve put two first-line nuclear subs off the US coast in about 15 years."

While Pentagon officials declined to speculate about what weapons may be aboard the vessels, the submarines are not considered to be among the larger Russian submarines that can launch nuclear missiles.

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