The NATO military alliance, led by Europe, said it was bolstering its defenses on its eastern flank following a tension-raising Russian drone incursion into Polish airspace.

In the years since Russia invaded Ukraine, NATO has focused on defending its own territory first and resisted lower-level harassment from Russia, like acts of sabotage and intimidation.

A map shows where Russian drones were recovered in Poland after they were intercepted and shot down on Tuesday night.

Military forces from across Europe have started deploying to NATO's eastern flank in a new military activity called "Eastern Sentry."

Russia's electronic warfare capabilities are increasingly targeting GPS systems across Europe, causing disruptions to civilian and military aviation. A recent incident involving European Commission President Ursula von der Leyen's plane losing GPS navigation highlights the vulnerability.

A restricted zone in the eastern part of the NATO country is in place following Russian drones entering its airspace.

There are a number of signs that have been highlighted by experts warning of a potential Russian invasion of NATO territory, including the Baltic states, Poland and possibly Germany

Ukraine is not a member of NATO, though the international security alliance has been a key player in its ongoing conflict with Russia, which escalated to a full-scale invasion by Russian forces Thursday. Since the United States helped form NATO, or the ...