While the hunt for the unidentified craft believed to be hiding somewhere in the Stockholm archipelago has dominated international headlines, increased Russian naval activity in the Baltic is nothing new, the Latvian Defense Ministry said in a statement.
"The Ministry of Defense has already noted that during the last year Russian naval activity in the Baltic close to Latvian territorial waters has significantly increased.
"Since July, navy patrol vessels have been on elevated alert for the purpose of early identification of suspect surface or underwater activity," the ministry said.
Coast Guard ships were being used to identify vessels and could deliver swift reports of any suspicious activity to the military, the statement said.
"It should be emphasized that Latvia has a modern maritime surveillance system and new patrol vessels, which allows an effective response... These capabilities have so far shown that Latvia has been able to identify and follow suspicious underwater activities," the ministry said.
However, new sensor systems might become necessary in light of events across the Baltic, the statement concluded.