(CNN) -- There are fears of Russians and it is October, but it's not a Tom Clancy novel. It is a case of international naval intrigue off the Swedish coast that brings back memories of the Cold War. The Swedish military on Monday intensified a search in the ocean off Stockholm for an underwater mystery vessel, but stopped short of calling it a submarine. Civilian vessels were ordered to stay at least six miles (about 10 kilometers) away from the Swedish warship conducting the search, the English-language website The Local reported. The search began Thursday after Swedish intelligence picked up an emergency radio call in Russian, reported The Local, citing the Swedish newspaper Svenska Dagbladet.
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Emergency radio call picked up by Swedish military, report says
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Radio transmissions sent to Russian enclave on Baltic Sea, report says
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Russia denies any vessel in Swedish waters
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Russian military has been active around world this year
On Monday, the @placeholder military vowed to continue searching at least for the next few days, according to The Local.