Drones spotted over sensitive infrastructure and facilities linked to the military in the northern German state of Schleswig-Holstein appear to have been sent deliberately to survey the area, Der Spiegel magazine reported, citing an internal government report.

The drone incursions come directly after a string of similar drone sightings near airports and military sites in neighbouring Denmark and Norway.

Suspicion has fallen on Russia, although Moscow has rejected the allegations.

Germany's Interior Minister Alexander Dobrindt said Germany needs to "find new responses to this hybrid threat", including greater capabilities to detect, assess and potentially shoot down such aircraft.

"Much of what we see today can be viewed as provocation -- and this is also how we assess the incidents we saw last week in Schleswig-Holstein," Dobrindt said.

Dobrindt last week announced that Germany is planning to create a new "drone defence centre" that will pool the expertise of Germany's federal and state governments.

He also said he wants to revise air safety laws to allow the "shooting down of drones" by the armed forces.

According to Der Spiegel, drones were first spotted hovering over a naval shipyard facility belonging to Thyssenkrupp Marine Systems shortly after 9:00 pm local time on Thursday.

Other facilities apparently scouted by the drones included a coastal power plant, an aviation fuel refinery and the Kiel Canal, according to the report.

Der Spiegel reported that suspicious drones had also been sighted over a German military base in the town of Sanitz on Thursday, and over the naval command in the nearby city of Rostock on Friday.

EU leaders are set to discuss bolstering Europe's defences at a summit in Copenhagen from Friday.