Germany has launched an investigation after becoming the latest European nation to report drone sightings over critical infrastructure. Authorities are investigating claims that unidentified drones may have spied on areas in Germany’s northernmost state.

A state official confirmed there had been a number of sightings late last week amid concerns Russia could be responsible for a flurry of drone incursions across Europe. Regional Interior Minister Sabine Sütterlin-Waack said flying objects of “various types and sizes” had been seen over both key infrastructure and military sites. The incidents happened over the district of Rendsburg-Eckernförde and the city of Kiel, within Schleswig-Holstein which borders Denmark.

An internal memo, cited by Der Spiegel, said a "combined drone system with a parent drone" was spotted over the university hospital.

Similar formations were then also reportedly spotted over a coastal power plant and the Kiel Canal — a major shipping route that links the North Sea and Baltic Sea.

Two small drones had earlier been seen over a shipyard in Kiel belonging to warship maker TKMS.

Further suspicious drones were reportedly spotted in the Mecklenburg-Western Pomerania state to the east.

UAVs were observed over a military base in Sanitz on Thursday, before a similar incident occurred over a naval command in Rostock the next day, per Der Spiegel.

Drone sightings have also caused disruption to airports in Norway and Lithuania over the past week.

On Wednesday, the French military boarded an oil tanker which some suspect could have been used as a launchpad for last week’s drone flights over Denmark.

Emmanuel Macron said the ship, anchored off the coast of Saint-Nazaire in western France, had committed “very serious wrongdoings” and linked the vessel to Russia’s so-called shadow fleet which is used to avoid Western sanctions over Moscow’s war in Ukraine.

The tanker was sailing off the coast of Denmark last week and was cited by European naval experts as possibly being involved in drone flights across the NATO nation.

Moscow has denied any involvement in the incidents and said it had no information about the ship.

Last month, Russia was accused of “reckless” violations of NATO airspace by fighter jets and drones.

EU leaders discussed the idea of a drone wall on Wednesday in response to the breaches.