COLOGNE, Germany — Russian civilian vessels may be employed by Moscow to spy on critical military infrastructure of NATO members, according to a new report by an Estonian intelligence service.

The annual assessment paints a picture of Russia ready to risk a large-scale war with NATO when any of its immediate neighbors, especially Belarus, are seen as getting too cozy with the West. According to the analysis, the Kremlin is equally jumpy when it comes to the Baltic states, considering the former Soviet-bloc countries as legitimate NATO targets in the event of an actual war.

“Even though the likelihood of a worst-case scenario is slim, surprises arranged by its authoritarian regime cannot be excluded,” the report by the Estonian Foreign Intelligence Service states, referring to the Russian government.

The Estonian intelligence assessment asserts that Russian civilian vessels are widely used as fronts for national security missions. For example, it cites cases when Russian research ships were observed to be acting especially curious to explore areas where alliance military drills are held.

“Attempts to enter foreign territorial waters without permission, under the pretext of needing shelter from storm or technical repairs, are becoming more and more frequent,” the document states. “This kind of behavior clearly stands out in comparison with other ordinary civilian vessels.”

According to the report, a leftover policy from Soviet days still requires the crews of civilian Russian-flagged vessels to perform “national assignments” when called upon, and they are expected to report information on events at sea and in foreign ports to the Russian Navy.

“Russia’s civilian fleet, then, is a kind of extension of its state authorities,” the Estonian intelligence service claims. “When needed, it can be used to gather information, to pursue military objectives, or to carry out covert operations. More attention should be paid to civilian vessels sailing under the Russian flag, particularly to the conditions under which they are allowed to enter the territorial waters and stay in the ports of other countries.”

The Estonian assessment comes as relations between NATO and Russia have deteriorated considerably, especially since Moscow’s annexation of Ukraine’s Crimea in 2014. Both sides have since dusted off Cold War-style weapons projects and war-fighting doctrine, signaling that the freeze in relations is here to stay.

The Baltic nations of Estonia, Lithuania and Latvia are especially fearful of Russian military adventurism on NATO’s eastern front, fearing that Moscow could use covert tactics to trigger a conflict in their countries.