A has been spotted in British waters off the coast of the Isle of Man, according to reports.

It is believed to be loitering over underwater infrastructure in the Irish Sea and is being closely monitored by a P-8A aircraft, .

The - often described by Western intelligence as a spy vessel - is a Project 22010-class intelligence ship operated by the , equipped with advanced capabilities for deep-sea missions.

The 107-metre long ship was also seen sailing through the English Channel earlier in the week.

The confirmed it was aware of the Russian ship's presence and was closely following its movements.

In a statement, they said: "The UK military routinely monitors UK territorial waters and the adjacent sea areas to ensure compliance with maritime law, to deter malign activity and to protect our national interests."

A Poseidon patrol aircraft was recently sent from RAF Lossiemouth to track the Yantarin an area between Devon and Cornwall, according to the .

Before sailing into British waters, the Yantar spent time off the coast of Norway, near Andøya Space Port.

At the time, the US and Norwegian militaries were carrying out exercises involving personnel from the USS Harry S Truman.

The Yantar entered service in 2015 and has often been observed close to important undersea telecommunications routes and infrastructure.

Acting as a mothership for specialised submersibles, it can deploy the Rus-class and Konsul-class mini-subs, which are capable of reaching depths of up to 6,000 metres (around 20,000 feet).

This remarkable range gives Yantar access to telecommunications cables stretching across seabeds worldwide.

The United States claims it has recently detected increased Russian military activity around key undersea cables.

Undersea cables play a key role in many aspects of modern society, accounting for the vast majority of digital communication.

This includes internet traffic and more than US$10 trillion in daily worldwide financial transactions.

Hundreds of undersea cables run across the world's seas and oceans, with cables in the Atlantic Ocean and the North Sea seen as being particularly at risk from potential Russian sabotage.

The world's critical undersea infrastructure is largely unguarded and its exact positions are available in the public domain, creating a potentially tempting target for the Kremlin.