Russia believes some NATO members, in particular Poland, want to abandon restrictions on the deployment of nuclear weapons in their countries, which would aggravate “strategic risks” and tensions, Russian foreign ministry spokeswoman Maria Zakharova said.

Russia appears to have been deterred by NATO's firm response last month to incursions into Polish and Estonian airspace, but Moscow is expected to continue testing boundaries, the U.S. general serving as NATO's top commander said on Tuesday.

Recent Russian drone violations into NATO airspace have sparked a new sense of urgency for the alliance to acquire low-cost defenses.

A book by German political analyst Carlo Masala, "If Russia Wins," outlines how Moscow might make a grab for Estonia in 2028.

"What a change from the 1984 Tom Clancy novel The Hunt for Red October. Today, it seems more like the hunt for the nearest mechanic," NATO Secretary General Mark Rutte said.

A Dutch F-35 has a drone-shaped kill marking after engaging Russian drones over Poland.

A former senior Nato commander and naval expert has told Westminster politicians that a united Ireland would pose a strategic threat. The loss of the protection afforded by the North would deepen the threat to Britain from Russia and China, Rear Admiral Chris Parry told MPs and members of the House of Lords in a briefing on Wednesday.

An investigation suggests Russian spy units may have used the MS Estonia site in the Baltic for listening to NATO vessel activities undetected.