The Royal Navy found some devices planted on the sea bed while several washed ashore, the newspaper reported.

Military and intelligence chiefs believe they were planted to gather intelligence on the UK's four submarines that carry nuclear missiles.

"There should be no doubt, there is a war raging in the Atlantic. This is a game of cat and mouse that has continued since the ending of the Cold War, and is now heating up again," a senior UK miliary figure told the paper.

The newspaper's three-month investigation said it had discovered unmanned Russian vehicles "lurking next to deep-sea communications cables".

The government also had "credible intelligence" that Russian oligarch-owned superyachts may have been used to conduct underwater reconnaissance, said the report.