An E-3 AWACS airplane assigned to NATO Air Base Geilenkirchen, Germany, flies over Romania in 2022. NATO is stepping up its air surveillance along Romania’s border with Ukraine. (Imani West/U.S. Air Force)

STUTTGART, Germany — NATO is stepping up surveillance along Romania’s border with Ukraine, a move that comes after reports that a Russian drone last week crossed into allied airspace.

U.S. Army Gen. Christopher Cavoli, NATO’s supreme allied commander, authorized the mission, which began Monday with increased flights by the alliance’s far-seeing AWACS aircraft.

The flights over Romania are in line with a broader effort to reinforce allied presence in the region and monitor what the Russian military is doing.

“It will also strengthen Romania’s ability to respond to the increased air activity in the vicinity of its border,” Allied Air Command said in a statement Monday.

NATO said the flights will take place solely over alliance territory and will operate out of Preveza Air Base in Greece and the NATO AWACS main base at Geilenkirchen, Germany.

Last week, Romania’s defense ministry reported that a Russian drone briefly crossed into its airspace in connection with an attack in neighboring Ukraine.

In response to the Sept. 27 incident, Romanian and Spanish fighter jets taking part in a NATO air policing mission in the country were scrambled to monitor the airspace.

The increased presence in Romania of the AWACS aircraft, known as NATO’s “eye in the sky,” will give the alliance the ability to look far into Ukraine to monitor events.

Sensors in a radar dome atop the planes can detect other aircraft out to a distance of 250 miles.