A FARTING whale is thought to have sparked fears that Russian drones were targeting UK nuclear subs.

The suspected blow-offs were picked up twice by Navy sensors scanning the area for signs of enemy activity.

It raised concerns that one of Vladimir Putin’s drone subs had dropped a listening device on to the seabed between the Isle of Raasay and Applecross in North West Scotland.

But a Naval official told The Sun: “We have been analysing the sounds and now believe it was a marine mammal. A whale.”

However, another source said they were still worried, adding: “We are taking it very seriously. We have to assume the worst.”

The sound was first detected travelling north from the range towards open sea. It came back days later and moved south towards the Skye Bridge before turning round and leaving.

At first, analysts described them as man-made sounds which had never been picked up on the range in its 55-year history.

It was feared that Russia’s deep sea research unit, known as GUGI, was trying to record acoustic signatures of our subs — making them easier to track and putting crews in danger.

And this week two civilian ships equipped with undersea robots were spotted at work in the 1,000ft-deep channel.

However, whale trumps have been mistaken for enemy subs in the past.

The alert came as Defence Secretary John Healey yesterday warned that Russian ships which damage British underwater cables faced being boarded and seized by Marines.

In November a Navy sub surfaced next to a Russian spy ship loitering over critical undersea infrastructure in the English Channel.

A Navy spokesperson said: “We constantly monitor territorial waters to protect the UK.”