A Ukrainian drone attack last weekend likely damaged around 10% of Russia's strategic bomber fleet and hit some of the aircraft as they were being prepared for strikes on Ukraine, a senior German military official said.

Germany has given Ukraine the green light to strike targets inside Russia using long-range weapons supplied by Berlin, in a decision that signals a notable hardening of Western resolve as the war grinds on.

Germany's chancellor said his government will lift all range restrictions on weapons it sends to Ukraine, being the last major western ally to do so.