The Ministry of Defence called in Nato spy planes to help hunt in the hunt for a foreign submarine off the west coast of Scotland, it has been reported.
At the height of the operation, five aircraft from four different nations with Royal Navy warships were involved in the search for the mystery vessel, according to a report by Aviation Week.
However the report said that it was unclear whether they succeeded in locating the submarine, or whether any foreign submarine had entered UK territorial waters.
The Ministry of Defence (MoD) confirmed that it had received assistance from Nato allies but would not say whether they had been searching for a submarine.
The hunt was said have been launched after a periscope was spotted in waters where Royal Navy submarines normally surface as they head into or out of their base at Faslane late last month.
At one point it involved two US Navy P-3 Orion aircraft, a CP-140 Aurora from the Royal Canadian Air Force and a French navy Dassault Atlantique 2, operating out of RAF Lossiemouth.
An RAF Sentinel radar-reconnaissance aircraft was also said to have taken part in the operation which appeared finally to have drawn to a close last week.
Since the Government scrapped its Nimrods in the 2010 Strategic Defence and Security Review, the UK has lacked a specialist maritime patrol aircraft.
A MoD spokesman said: "Nato partners have provided assistance for the operation of maritime patrol aircraft from RAF Lossiemouth for a limited period with the Royal Navy. We do not discuss the detail of maritime operations."
The incident comes just weeks after Sweden mounted a search for a suspected Russian submarine thought to be operating in its territorial waters.
Although the hunt was unsuccessful, defence officials said there was no doubt that their waters had been violated by a foreign power.
Last month the Royal Navy tracked four Russian warships passing through the English Channel while there has been a recent upsurge incidents of Russian long-range bombers approaching UK airspace.
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules hereComments are closed on this article