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 struck overnight a Russian oil depot that serves a military airfield in the Russian city of Engels, Ukraine's military said on Wednesday.

The Ukrainian military said Wednesday that it struck a fuel storage depot deep inside Russia, causing a huge blaze at the facility that supplies an important Russian air base. Russian officials acknowledged a major drone attack in the area,

"Such fire damage is an integral part of combat operations of Ukraine's Defense Forces units, which are engaged in combat operations on the territory of the Russian Federation," the General Staff of Ukraine's Armed Forces said.

Kursk could be used as a bargaining chip in any future peace negotiations, it has been suggested.