The UK intercepted a Russian submarine on its way to the English Channel

The Royal Navy's HMS Kent intercepted the Stary Oskol, a Russian Kilo-class submarine capable of carrying torpedos and anti-ship cruise missiles on Tuesday evening, the Guardian reports.

HMS Kent's commanding officer, Cmdr Daniel Thomas, said: "Locating this submarine was a combined effort with NATO allies and shadowing such units is routine activity for the Royal Navy," the Guardian reports.

The Stary Oskol, a diesel-electric submarine, can go nearly silent when submerged and operating on stored electric power, making it difficult to detect.

This incident represents just one in a long line of Russian military planes and ships encroaching on UK and NATO territory. The trend has become prominent enough that Vice Admiral James Foggo III of the US Navy characterized the uptick in Russian submarine activity as the beginning of a "fourth battle of the Atlantic."

According to Foggo, Russian submarine activity is at it's highest level since the Cold War, and that should be cause for concern.

"Once again, an effective, skilled, and technologically advanced Russian submarine force is challenging us. Russian submarines are prowling the Atlantic, testing our defenses, confronting our command of the seas, and preparing the complex underwater battlespace to give them an edge in any future conflict," Foggo wrote in the June issue of Proceedings, the US Naval Institute's monthly publication.

"Not only have Russia's actions and capabilities increased in alarming and confrontational ways, its national-security policy is aimed at challenging the United States and its NATO allies and partners," Foggo continued.

In his piece, Foggo specifically mentioned the Kilo-class of Russian subs: "Russia rapidly is building and deploying more advanced and significantly quieter attack submarines and frigates armed with the long-range Kalibr cruise missile (including six new Kilo-class diesel-electric attack submarines destined for the Black Sea)."

"As demonstrated last December by Kalibr launches into Syria from the Eastern Mediterranean, Russian leaders will use such weapons at will, without the same qualms we have about collateral damage," said Foggo.

Though the RAF and NATO forces spotted and intercepted this submarine in particular, the threat remains that there are more, unidentified Russian subs patrolling valuable underwater infrastructure, such as oil rigs and telecommunication lines that the US and NATO forces desperately rely on.