Russian submarines and spy ships appearing near vital undersea data cables that carry massive amounts of global communications have U.S. officials concerned that the country could threaten to cut the lines in a crisis, crippling the backbone of most of the global Internet.

These new concerns were reported by The New York Times on Sunday, citing private conversations with U.S. military commanders and intelligence officials who have monitored "significantly increased Russian activity along the known routes of the cables," through which more than 95 percent of global communications and more than $10 trillion worth of global commerce travel on a daily basis.

There is no evidence of any cable cutting so far. The concerns reflect a growing worry among senior U.S. officials and allies over the increased military activity of Russia around the globe.

Experts would only speak on the record in general terms about Russia's activities, with Navy spokesperson Cmdr. William Marks saying, "It would be a concern to hear any country was tampering with communication cables; however, due to the classified nature of submarine operations, we do not discuss specifics."

Rear Adm. Frederick J. Roegge, the Navy's Pacific submarine commander, simply stated, "I'm worried every day about what the Russians are doing."

In private, more than a dozen U.S. officials confirmed that the Russian Navy's operations near the vital fiber-optic data cables had become a "source of significant attention in the Pentagon," a modern-day parallel to the wary relationship between the U.S. and Russia during the Cold War. In those days, the chief concern was the Russians might tap into communications cables for intelligence purposes.

However, the current alarm is more troublesome: The Russian military could sever the crucial Internet-carrying cables at some of the deepest and most difficult points to access, essentially halting the communications of Western governments, economies and citizens with no backup and no quick fix.

While undersea communications cables can and do get cut by accident or because of natural disasters, usually those cuts are in shallow areas near the shore, making for a relatively easy repair that takes just a few days.

The Russians, however, appear to be looking for vulnerable access points at far greater depths, where repairs would be much more difficult. On top of that, there are worries the Russian Navy could threaten to sever the lines covertly, leaving the U.S. or its allies without any idea of where to begin repairs.

Some of the known international data cables connecting the global Internet. (Screenshot : Greg's Cable Map / www.cablemap.info)

"The risk here is that any country could cause damage to the system and do it in a way that is completely covert, without having a warship with a cable-cutting equipment right in the area," said Michael Sechrist, former manager of a Defense Department-funded Harvard-M.I.T. research project. Some experts also added it is possible Russia's increased activity involves searching for secret U.S. military data cables, the locations of which are not publicly available.

The Pentagon's concerns come after the Yantar -- reportedly a Russian spy ship equipped with two deep-sea submersibles capable of diving miles down under the water and cutting cables -- was monitored by the U.S. cruising slowly off the East Cost of the U.S. toward Cuba. That's where a major fiber-optic line connects from the mainland to the U.S. Naval base in Guantanamo Bay.

Russian officials insist the Yantar is an oceanographic ship not tied to Russian intelligence services.

"The Yantar is equipped with a unique onboard scientific research complex which enables it to collect data on the ocean environment, both in motion and on hold," said the head of deepwater research at the Russian Defense Ministry, Alexei Burilichev, to SputnikNews recently. "There are no similar complexes anywhere."

But commander of U.S. naval forces in Europe Adm. Mark Ferguson countered, saying the operations fit into Russia's emerging strategy of hybrid warfare, mixing conventional force with Special Operations missions with 21st century tools and objectives.

"This involves the use of space, cyber, information warfare and hybrid warfare designed to cripple the decision-making cycle of [NATO]," he said.

Intelligence experts' next concern about the Russian Navy's 21st century strategy is Russia is reportedly building an unmanned, undersea drone that's capable of carrying small tactical nuclear weapons to coastal areas.