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.

One of Ukraine's largest cities, Kharkiv is located just a few dozen kilometres from the Russian border and has been under constant Russian shelling during more than three years of war. "Kharkiv is currently experiencing the most powerful attack since the start of the full-scale war,