Russian warships are understood to have twice recently come close to a Finnish marine research ship operating in the Baltic Sea.
The research vessel Aranda was understood to be in international waters during the incidents, which have prompted senior Finnish officials to consider making a political response.
On the first occasion, in August, an unidentified Russian vessel twice urged Aranda to change course.
In September, the Steregushchiy-class guided-missile frigate Boiky sailed close enough for both it and its helicopter – which flew nearby – to be photographed by Aranda ‘s crew.
Initially, the Finnish Foreign Ministry said there was no need for diplomatic action or an explanation as the Aranda was not put in danger.