Drones have been spotted in recent days flying over airports in Denmark and Norway, causing some of them to close temporarily. There was also a drone sighting over Denmark's biggest military base late Friday.

Germany, one of Ukraine's key backers in its fight against Moscow, has also reported a rise in suspicious drone sightings in recent times -- the latest came late Friday in a northern state bordering Denmark.

Suspicion has fallen on Russia, even if no definite proof has been made public.

Berlin had already announced plans to bolster its drone defence systems earlier this week to counter the growing Russian threat.

Tabloid Bild reported that, among measures planned, the government was considering allowing the armed forces to shoot down drones under certain conditions.

The military should be able to intervene if a drone poses a serious danger to human life or critical infrastructure and other measures would be insufficient, the paper said.

In such cases, decision-making powers would reportedly be transferred to the defence ministry. Such powers currently lie with the police.

Contacted by AFP, the interior ministry did not confirm the plan.

But speaking to the Rheinische Post newspaper, Interior Minister Alexander Dobrindt said that he wanted to overhaul air security laws so the military can help the police "especially in drone defence".

"We are not only experiencing a turning point in military security, but also in civil defence and civil protection as a whole," he said.

Late Friday, drones were spotted over northern Schleswig-Holstein state, which borders Denmark, state interior minister Sabine Suetterlin-Waack told local broadcaster NDR.

Investigations were ongoing into the incident. Authorities did not say how many drones were spotted, or exactly where.