Germany is Ukraine's second biggest military backer after the United States.

"In terms of personnel and material, Russian armed forces are likely to be capable of carrying out an attack against NATO by the end of the decade at the latest," BND foreign intelligence chief Bruno Kahl told parliament.

A direct confrontation between Moscow and the US-led military alliance was "becoming an option for Russia", Kahl said.

Kahl spoke at a hearing in the Bundestag alongside the heads of Germany's domestic and military intelligence, who took turns to warn of the growing threat from Russia in the context of the invasion of Ukraine.

"Russian espionage and sabotage in Germany are increasing, both qualitatively and quantitatively," domestic intelligence chief Thomas Haldenwang said.

He listed suspected sabotage activities, including a near miss involving an exploding package and a DHL cargo plane.

The parcel burst into flames on the ground before being loaded into the plane, in what Haldenwang called a "lucky accident", without explicitly naming the suspected culprits.

"If it had exploded onboard during the flight, there would have been a crash and the debris could have hit all the people here in Germany who, openly or secretly, sympathise with Putin," he said.

Russia was also engaged in disinformation campaigns, had deployed drones to spy on sensitive locations and was looking to recruit people, including from the world of organised crime, with offers of money, Haldenwang said.

There had also been a "significant increase" in espionage and sabotage activities from Russia targeting the German armed forces, the head of military intelligence Martina Rosenberg said.

Among the activities undertaken by Russia were "reconnaissance of German arms deliveries to Ukraine" as well as surveillance of military training and armaments projects, she said.