The head of Germany's foreign intelligence service BND warned of increasing hybrid attacks by Russia on Germany and the NATO defence alliance, with the underlying goal of testing the alliance in the hopes that it would fail.

Speaking at an event held by the German Society for Foreign Policy in Berlin, Bruno Kahl said BND experts believe high-ranking officials in the Russian Ministry of Defence apparently harbour doubts about whether NATO's mutual defence commitments and the US's extended deterrence in Europe would hold in a serious situation, he explained.

"Currently, there is no evidence of concrete war intentions by Russia. But if such views gain ground in the government headquarters in Moscow, the risk of a military confrontation also grows in the coming years."

Kahl does not believe Russia would engage in such a confrontation to gain territory, but rather to quash NATO.