German authorities said Friday that unidentified drones had been spotted flying over sensitive military and industrial sites including the US Ramstein airbase.
The reports come after German officials have repeatedly voiced alarm about the threat of Russian spying as the Ukraine war heightens tensions between Moscow and NATO.
However, police did not say who they thought had launched the unmanned aerial vehicles.
“In recent days, several drone flights have been detected over critical infrastructure in Rhineland-Palatinate state,” a regional police spokesman told AFP.
The UAVs were first sighted at German company BASF’s plant in Ludwigshafen, known as the world’s biggest chemicals complex, the spokesman said.
“This was followed in the course of this week by drone overflights over the US airbase in Ramstein,” he added.
The drones were detected at dusk and were “larger than the usual commercial hobby drones,” the spokesman said.
Police in Rhineland-Palatinate have set up a special investigative unit to look into the incidents.
There is “no concrete danger to the facilities concerned,” the spokesman said.
The sightings in Ramstein were on December 3 and 4, according to Der Spiegel magazine.
Unidentified drones have also been sighted over facilities belonging to German arms maker Rheinmetall, Der Spiegel reported, citing security services.
A source with knowledge of the matter confirmed to AFP that suspicious drones had been spotted near Rheinmetall’s largest ammunition production site at Unterluess, Lower Saxony.
Unidentified drones were also reported in August over the Bruensbuettel industrial area in the northern state of Schleswig-Holstein.
Foreign Minister Annalena Baerbock at the time said the devices were surely “not there to observe the beautiful local landscape, but because there is a chemical park there and a… storage facility for nuclear waste nearby.”
Media reports said officials believed those drones were Russian reconnaissance devices.
However, investigations into the Bruensbuettel sightings have so far shown no indications of espionage, according to a report from the ARD broadcaster on Friday.
German officials have repeatedly raised the alarm in recent months about Russian spying and “hybrid warfare,” including acts of sabotage and disinformation in the campaign towards February general elections.