Ukrainian drones struck deep inside Russia in an overnight attack targeting an oil facility serving a military airfield in the city of Engels, nearly 400 miles from the border, Ukraine’s military said Wednesday.

Ukraine's armed forces said Wednesday they attacked a strategic Russian oil depot overnight used to provide fuel for strategic bombers. A huge fire erupted at the Kombinat Kristall depot in the Russian city of Engels.

Russian authorities have declared a state of emergency in the Volga River port city of Engels as a huge fire, caused by a “massive” Ukrainian drone attack, rages unchecked. The strike was on the strategically important fuel storage tank farm for Engels Air Base,