"Eastern Sentry is not just a new initiative – it is a clear signal: NATO’s borders are inviolable, and the security of our citizens remains a priority," Poland's General Staff wrote on X.

Alarms bells sounded this week in Europe after NATO jets scrambled to intercept an unprecedented Russian drone incursion in Poland. Now there is fresh unease on NATO’s eastern flank, as Russia and Belarus kick off major military drills to test the readiness of their armed forces.

NATO on Friday launched an operation named Eastern Sentry to bolster the defence of Europe's eastern flank in response to Russian drone incursions into Polish airspace earlier this week, Secretary-General Mark Rutte said.

The U.S.-led military alliance said it would bolster defenses along its eastern flank after the incursion, the first of its kind since the Ukraine war began; Russia denied targeting Poland.

The incident represented the most serious spillover of the war in Ukraine for NATO, as its aircraft engaged the drones that it said came from Russia.

By Barbara Erling BRANIEWO, Poland (Reuters) -Six kilometres from the Russian border in northern Poland, office administrator Agnieszka Jedruszak is digging a trench. Driven by fear of war with Russia,

NATO will launch a new deterrence initiative called "Eastern Sentry" in response to Russia's drone attack on Poland, the military alliance's secretary general Mark Rutte announced on Sept. 12.

European leaders on Thursday expressed alarm over growing Russian hostility threatening their countries as Moscow's forces pursue their invasion of Ukraine -- concerns exacerbated by events of the previous day when multiple Russian drones struck Polish soil.

Sept 12 (Reuters) - Russia and Belarus began a major joint military exercise on NATO's doorstep on Friday at a time of heightened tension with the Western alliance, two days after Poland shot down Russian drones that crossed into its airspace.

Some of Kyiv's allies in NATO are discussing sending troops to Ukraine as part of security guarantees after Russia's war ends.

They are intended to showcase close defense ties between Moscow and Minsk, as well as Russia’s military might as it fights its 3½-year-old war in neighboring Ukraine.