article_snippet.sent: Finland, which shares an 833-mile  border with Russia, has been increasingly worried about Russia powerful neighbour after a year of Russian air force sorties and military border exercises.
article_snippet.sent: Finland defence minister Carl Haglund did not say whether Russia was involved but told local media that it was extremely rare for the military to use such warning charges.
article_snippet.sent: The Finland incident comes just months after Sweden's armed forces hunted unsuccessfully for what Sweden's armed forces believed to have been a foreign submarine close to Stockholm .
article_snippet.sent: It comes just months after Sweden suspected Russia of sending a vessel into waters close to the capital HelsinkiStockholm.
article_snippet.sent: In what was Sweden's biggest mobilisation since the Cold War, Russia navy hunted unsuccessfully for a week for what its navy believed to be a foreign submarine after several observations were made.
article_snippet.sent: Swedish officials never blamed any country, though most defense analysts said Russia was a likely culprit.
article_snippet.sent: Today Finland defence minister Carl Haglund did not say whether Russia was involved but told local media that the target could have been a submarine, and that the target has likely left the area, adding that Finland has rarely used such warning charges.
article_snippet.sent: Finland defence minister Carl Haglund said: 'We strongly suspect that there has been underwater activity that does not belong there.
article_snippet.sent: Of course it is always serious if our territorial waters have been violated,' Finland defence minister Carl Haglund told Finnish news agency STT.
article_snippet.sent: Moscow retorted immediately, saying moves by Finland and Sweden towards closer ties with NATO were of 'special concern'.
article_snippet.sent: Reports of a submarine spotted off Stockholm last year led to Sweden's biggest mobilization since the Cold War.
article_snippet.sent: Regional tensions were reflected earlier in April after an unprecedented hawkish joint statement by Nordic countries - Sweden, Norway, Finland, Denmark and Iceland - that directly cited the Russian 'challenge' as grounds to increase defense cooperation.
highlights_snippet.sent: Experts believe a foreign object is likely to have been a Russian submarine .