US officials were reported to be aware of the movements, which could be an effort to intimidate Britain over its support for Ukraine or to identify weaknesses in British and Irish defence.

It would be difficult for a Russian submarine to navigate the Irish Sea without breaking international law because legally they can only travel on the surface of territorial waters.

The varying depths of the Irish Sea would make it difficult for a Russian vessel to travel in the waters submerged, Bloomberg reported.

The deployment of Russian submarines in waters around Britain and western Ireland during the war in Ukraine was known. However, it had not been previously reported that they had travelled in the Irish Sea which separates Britain from Ireland.

Irish media reported that a British warship and helicopter chased off a Russian submarine outside Cork Harbour in the south west of Ireland. The UK reportedly stepped in because Irish forces could not meet the underwater threat in Cork, which is the landing point for an undersea cable linking the UK and Canada.

Last month, the BBC reported that a Russian submarine had been spotted off the coast of Scotland before travelling on to Cuba. At the same time Russian state media reported that navy assets, including the Yasen-class Kazan submarine, conducted drills in the Atlantic Ocean before visiting the Caribbean country.