Air assaults on Saturday killed at least four people. Kharkiv’s mayor described an overnight strike as “the most powerful attack” since the beginning of the war.

Russia has hit Ukraine's second-largest city, Kharkiv, with a massive drone and bomber attack, killing four people and injuring nearly 60, officials say. Two people were also killed in Russian strikes on Kherson, in southern Ukraine, local authorities said.

With one surprise attack after another, Ukraine keeps inventing new ways to wage war with drones. In turn, Russia is building a massive drone army of its own.