The air force said on its Whatsapp communication channel that its Quick Reaction Alert (QRA) was activated at the Laage airbase near Rostock, on the Baltic coast in the northeast.

"The reason was an unknown aeroplane over the Baltic Sea, which was flying without a flight plan or activated transponder," the air force said in the message, which confirmed an earlier press report in Bild.

German Eurofighter jets were scrambled to identify the Ilyushin Il-20 reconnaissance plane, which was subsequently "escorted" back towards the Russian exclave of Kaliningrad, from where it was first tracked.

Bild said the Russian aircraft was found early Thursday east of the German Baltic island Rugen from where it was heading towards "German air space".

The fact that the aircraft's transponder was deactivated presented "a considerable danger to civilian air traffic," Bild said.

Military sources quoted by Bild said that Russian reconnaissance planes were occasionally identified off the German coast.

Many NATO nations have a QRA system to help protect their air space.

Tensions over the Baltic Sea have heightened since Russia's full-scale invasion of Ukraine in 2022.