NATO spy planes arrive in Romania on Tuesday to strengthen the eastern flank of the military alliance and monitor Russia's military activities, Reuters reported.

NATO had earlier announced that it would send long-range airborne early warning and control system (AWACS) reconnaissance aircraft to Bucharest, where they would begin conducting reconnaissance flights exclusively over NATO territory.

The planes bound for Romania belong to a fleet of 14 NATO reconnaissance aircraft, usually based in Germany. About 180 troops will be deployed to support the planes.

"As Russia’s illegal war in Ukraine continues to threaten peace and security in Europe, there must be no doubt about NATO’s resolve to protect and defend every inch of Allied territory," NATO spokesperson Oana Lungescu said in a Jan. 12 statement.