Ukrainian drones attacked targets in Tatarstan, a highly industrialised region southeast of Moscow, in the early hours of Tuesday and some people were injured, Tatarstan's head Rustam Minnikhanov said.
Russian electronic warfare defences intercepted a Ukrainian drone near Tatneft's Taneco refinery, one of Russia's biggest, in Nizhnekamsk, the RIA state news agency reported.
A fire broke out at the refinery that was extinguished within 20 minutes, RIA said.
Production has not been disrupted, RIA said.
Pictures from the scene indicated the drone hit the primary refining unit, CDU-7, at the Taneco refinery.
It was one of Ukraine's deepest drone attacks in Russian territory.
The Taneco oil refinery is one of Russia's largest and newest.
Its production capacity stands at around 360,000 barrels per day.
Tatarstan's Minnikhanov said that enterprises in Yelabuga and Nizhnekamsk were attacked.
Two drones attacked a dormitory on the territory of the Alabuga Special Economic Zone.
At least seven people were injured, Russian media reported.
"There is no serious damage, the technological process of the enterprises is not disrupted," Minnikhanov said.
Unverified footage on social media showed a loud blast followed by people running for cover.
The Washington Post reported in 2023 that Russia was mass-producing drones at a plant in the Alabuga Special Economic Zone.
A Ukrainian intelligence source told Reuters in Kyiv that "significant damage" had been done to a military target in Russia's Tatarstan region in an attack using Ukrainian-made drones.
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