US officials are growing concerned over the activity of Russian submarines and spy ships near undersea internet cables, The New York Times reports, fearing that they could be used to cut vital lines of communication. There is currently no evidence that Russia has severed any fiber-optic lines, which underpin most global communications, though military and intelligence officials tell the Times that they've observed increased Russian activity along cables in the North Sea, northeast Asia, and near American shores.

It's not uncommon for undersea cables to be damaged by ship anchors or natural disasters, and they're usually easy to repair. But the fear is that Russia may be targeting the cables at greater depths, where they're harder to monitor and fix, and that it may seek to disrupt them during times of conflict. Moscow may also be looking for secret cables that the US installed for military purposes.

"The level of activity is comparable to what we saw in the Cold War."

Russia's activity has become a point of concern at the Pentagon, adding to already mounting tensions between Moscow and the West. A senior European diplomat tells the Times: "The level of activity is comparable to what we saw in the Cold War."

Last month, the US tracked the Yantar, a Russian spy ship, as it travelled off the east coast toward Cuba. The ship carried two deep-sea submersible vehicles, which US officials say can be used to cut cables, according to the Times. One major cable lands near the US military base at Guantanamo Bay. Russia has said that the Yantar is an oceanographic ship used for scientific research.

Undersea cables have long been targeted for intelligence gathering; the US has a nuclear submarine dedicated to tapping them. They've also become vital to the global economy. According to the Times, the fiber-optic cables facilitate $10 trillion in daily global business, and carry more than 95 percent of global communications.