The BND said that its analysis of Russian budget data showed that in 2022 and 2023, military spending had been around 66 percent higher than officially reported.

"These figures are a concrete embodiment of the growing threat to Europe posed by Russia," the agency said in a rare public statement.

It said Russia's definition of defence spending differed from that used by NATO and excluded expenses such as military construction and IT projects or welfare payments to service members' families.

If these and other "hidden" amounts are taken into account, total spending in 2024 reached 202 billion euros ($171 billion) instead of the official 140 billion euros, it said.

For the first three quarters of 2025, the total jumps to 163 billion euros, as opposed to the officially reported 118 billion euros, according to the BND.

In the years running up to Russia's 2022 full-scale invasion of Ukraine, the "hidden" parts of the Russian military budget were almost as big as those which were officially declared.

The BND said that, taken together, military spending in 2025 represented around 10 percent of Russia's economic output and half of its total budget.

"These funds are not only being used for the war against Ukraine, but also for the additional build-up and expansion of military capabilities -- particularly near NATO's eastern flank," the BND said.

In October BND chief Martin Jaeger told lawmakers that Russia was determined to expand its "sphere of influence further westward into Europe".

"To achieve this goal, Russia will not shy away from direct military confrontation with NATO if necessary," Jaeger warned.

German Chancellor Friedrich Merz has accused Russia of sabotage, cyberattacks and espionage targeting Germany and other European countries.

Among other incidents, he has said, Merz suspects Moscow of being behind several mysterious drone flights that have caused chaos at European airports in recent months.