The NBS spotted a submarine support vessel of the 'Kashtan' class, coded SS-750, operating 11.5 nautical miles (21 kilometers) from Latvian territorial waters, NBS said.
Armed Forces on 27 NOV in LV EEZ 11,5 nmi from territ. waters spotted RU Navy's sub support Kashtan-class ship SS-750.— NBS (@Latvijas_armija) November 28, 2014
The sighting comes just days after a Russian submarine was itself spotted a little further out - 27 nautical miles from the maritime border.
When NBS reported the sighting, the Russian Ministry of Defense reacted in sarcastic terms, saying "Thank you for your continued PR campaign on behalf of the Russian Navy."
СМИ Латвии, вслед за шведскими коллегами, сенсационно сообщили о появлении в Балтийском море российской субмарины https://t.co/Uj9cMcrIhq— Минобороны России (@mod_russia) November 24, 2014
However given the concerns recently expressed by Sweden, which is convinced a Russian sub penetrated its waters close to Stockholm, covert Russian submarine activity in the Baltic Sea would appear to be no laughing matter.