A series of drone sightings over military and industrial sites in Germany in recent months has sparked alarm and the government said last month that military regulations will be changed to let troops shoot down suspicious unmanned aerial vehicles.

From January 9 to 29 six incidents involving suspicious drones flying over the Schwesing air base near the Danish border were recorded, the Suddeutsche Zeitung newspaper reported Saturday.

A military spokesman said the cases had been reported to Schleswig-Holstein state police but did not immediately make a direct link to espionage.

The Schwesing base is used for training forces using anti-air missiles and Ukrainian troops fighting Russia have been instructed there. Germany is a key military supplier for Ukraine.

According to Suddeutsche Zeitung, Ukrainian forces have been trained on using the US-made Patriot missile interceptors.

The spokesman acknowledged that reports of drones and "alleged espionage attempts" have increased in recent months.

But he indicated that the military was cautious about the motive for the incidents as drones could be bought in stores and "individuals also use drones over military buildings without thinking".

Germany, like other states in the region, suspects that Russia has launched undercover action against western countries as it pursues its invasion of Ukraine.

Several telecoms cables have been cut in the Baltic Sea in recent months and experts and politicians have blamed Russia. Moscow has denied any role in the cases.