A fire broke out overnight at a major Russian oil refinery in the southwestern Volgograd region, authorities said Saturday, after a drone strike claimed by Ukraine.
A Ukrainian defence source told AFP that Kyiv's SBU security service had "organised" the attack, which came after months of Ukrainian drone attacks against Russia.
"Last night, the air defence and electronic jamming repelled an attack by drones in the Volgograd region's Kalachyovsky and Zakanalye districts," governor Andrei Bocharov said on Telegram.
"A fire started at the Volgograd refinery after one of the downed drones fell," he said, adding that the fire service had already brought the blaze under control by the start of the morning.
No one was hurt, Bocharov said.
Russian emergency services later told local media the fire had been put out.
Kyiv, which used not to claim responsibility for such attacks, has changed tactic and now publicly takes responsibility.
"The fire at the refinery in Volgograd was 'organised' by SBU drones," a source in the Ukranian defence sector told AFP.
Russian energy giant Lukoil, which operates the refinery, says on its website that it is "the biggest producer of oil products in the federal South district", which covers eight regions of southwest Russia.
The plant is located south of the city of Volgograd.
Local media V1 published photos it said showed an overnight explosion during the attack, and residents told V1 that they heard two explosions.
The Russian army said electronic jamming had brought down or intercepted four drones in the region of Belgorod which borders Ukraine, two in Volgograd and one more in the Rostov-on-Don area.