Ukraine says its forces successfully hit an oil refinery in the Russian town of Kstovo, around 800 kilometres (500 miles) from the front lines in eastern Ukraine.
Four drones hit a Lukoil company depot, Ukrainian media said, adding that the facility suffered significant damage.
Videos posted on social media showed large flames rising over an industrial facility.
Regional governor Gleb Nikitin said that drone debris had fallen over the industrial zone, and that no casualties had been reported at the scene.
Separately, the governor of the region of Smolensk, Vasily Anokhin, said on Telegram that a "massive" drone attack against "civilian infrastructure" had occurred in his region, although no casualties were immediately reported.
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