Ukraine fired more than 40 drones into Russia’s bordering Rostov region, Moscow defence officials said on Friday, in what appeared to be one of its biggest air attacks in the war and as Kyiv’s forces step up their assaults on Russian soil.

Russia’s Defence Ministry said a total of 44 drones were “intercepted and destroyed” in the Morozovsky district, more than 100 kilometers (60 miles) from the border. The attack damaged a power substation, Rostov Gov. Vasily Golubev said.