A former Royal Navy chief has warned Britain is one mistake away from war with Russia.
Admiral Lord West also said there are more of their nuclear subs encroaching our waters than in the Cold War.
Defence sources claim up to three or more have been located off the west coast of Scotland, searching for our four Trident subs from HM Naval Base Clyde.
Lord West said: “Actively looking for our submarines becomes a very escalatory measure.
"Vladimir Putin wants to show he is a great player on the world stage but it’s extremely dangerous.”
Lord West, 72, also warned that a mistake, such as a mid-air collision between Russian and Nato aircraft, could get out of hand very quickly.
He said such an incident would lead to an increase in tension and no-fly zones. Russia already has more than 6,000 nuclear warheads.
Last month, General Sir Nick Carter, the chief of the defence staff, warned Russia was “flexing its muscles” in a way “not displayed since the Cold War”.
An MoD spokesman said: “The Royal Navy and RAF have a number of assets at high readiness to monitor UK waters and airspace, protecting our national security 24 hours a day, 365 days a year.”
