* Ships, helicopters, troops scour Stockholm archipelago
* Swedish media report Russian link, Moscow denies it
* Increasing tension in Baltic over perceived Russian threat (Adds Russian defense ministry comment)
STOCKHOLM, Oct 18 (Reuters) - Sweden beefed up its military presence in the Stockholm archipelago on Saturday to scour its waters for "foreign underwater activity," a mobilization of Swedish ships, troops and helicopters unseen since the Cold War.
The search in the Baltic Sea less than 30 miles (50 km) from Stockholm began on Friday and reawakened memories of the final years of the Cold War when Sweden repeatedly hunted suspected Soviet submarines along its coast with depth charges.
There is now increasing tension with Russia among the Nordic and Baltic states - most of them European Union members - over Moscow's involvement in the Ukraine crisis. Finland last week accused the Russian navy of interfering with a Finnish environmental research vessel in international waters.
The Swedish military has said information about suspicious activity came from a trustworthy source, without providing details, and that more than 200 military personnel were involved in the search.
The Swedish daily Svenska Dagbladet, citing unidentified sources with knowledge of the hunt, said it began after a radio transmission in Russian on an emergency frequency.
Further encrypted radio traffic from a point in the archipelago and the enclave of Kaliningrad, home to the Russian Baltic fleet's headquarters, was intercepted on Friday evening after the Swedish search started, the newspaper said.
The Russian Defense Ministry said on Sunday that there were no emergency situations in the Baltic involving its vessels.
"Russian Navy ships and submarines are fulfilling their duties in the world ocean waters in accordance with the plan," Interfax news agency quoted a ministry spokesman as saying. "There has been and there are no extraordinary, let alone emergency, situations involving Russian warships."
Countries in the Baltic Sea region have become increasingly wary of Russia's military ambitions since Moscow annexed Ukraine's Crimea region in March following the overthrow of Kiev's pro-Moscow president by protesters.
Last month, Sweden said two Russian warplanes entered its air space, calling the intrusion a "serious violation" and sending a protest to Moscow's ambassador in the Nordic country.
Ships, helicopters and troops from an amphibious unit as well as the home guard combed the search area in Stockholm's archipelago. The forces include HMS Visby, a corvette that has stealth technology and equipment for anti-submarine warfare.
The Swedish military said on Friday there had been no armed intervention and declined to comment on who might be responsible for the suspicious activity, or whether the report had been about a submarine.
"We still consider the information we received as very trustworthy," Captain Jonas Wikstrom, head of operations for the search, told reporters. "I, as head of operations, have therefore decided to increased the number of units in the area."
Should the search find proof of foreign military activity in Swedish coastal waters it will represent the first real test of Prime Minister Stefan Lofven's center-left minority government only weeks after coming to office.
In 1981, a Soviet submarine known under its Swedish designation U137 was stranded deep inside Swedish waters not far from a major naval base in the neutral country, sparking intense suspicion about the scale and motives of such incursions. (Additional reporting by Alexei Anishchuk in Moscow, Editing by Mark Heinrich)
Our 2024 Coverage Needs You
It's Another Trump-Biden Showdown — And We Need Your Help
The Future Of Democracy Is At Stake
Our 2024 Coverage Needs You
Your Loyalty Means The World To Us
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
The 2024 election is heating up, and women's rights, health care, voting rights, and the very future of democracy are all at stake. Donald Trump will face Joe Biden in the most consequential vote of our time. And HuffPost will be there, covering every twist and turn. America's future hangs in the balance. Would you consider contributing to support our journalism and keep it free for all during this critical season?
HuffPost believes news should be accessible to everyone, regardless of their ability to pay for it. We rely on readers like you to help fund our work. Any contribution you can make — even as little as $2 — goes directly toward supporting the impactful journalism that we will continue to produce this year. Thank you for being part of our story.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
It's official: Donald Trump will face Joe Biden this fall in the presidential election. As we face the most consequential presidential election of our time, HuffPost is committed to bringing you up-to-date, accurate news about the 2024 race. While other outlets have retreated behind paywalls, you can trust our news will stay free.
But we can't do it without your help. Reader funding is one of the key ways we support our newsroom. Would you consider making a donation to help fund our news during this critical time? Your contributions are vital to supporting a free press.
Contribute as little as $2 to keep our journalism free and accessible to all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. Would you consider becoming a regular HuffPost contributor?
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. If circumstances have changed since you last contributed, we hope you'll consider contributing to HuffPost once more.
Support HuffPostAlready contributed? Log in to hide these messages.