German military official says Ukrainian drone strikes significantly damaged Russia's bomber fleet and surveillance aircraft.

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,