The governor of Russia's Samara region said on Saturday that Ukrainian drones had struck two oil refineries belonging to state-owned oil giant Rosneft in the region, causing no casualties but leaving one facility on fire.
Russia is voting through Sunday in three-day presidential elections, with President Vladimir Putin on Friday accusing Ukraine of attempting to sabotage the polls he is certain to win.
The Volga river region's Syzran refinery was on fire but an attack on the Novokubyshev refinery was thwarted, Governor Dmitry Azarov said in a statement on the Telegram messaging app.
No casualties in the strike
He said workers at both plants had been evacuated and there were no casualties.
Unverified footage published online showed what appeared to be a major fire at the Syzran refinery, with emergency services working at the scene.
Ukraine has in recent weeks heavily targeted Russia's oil infrastructure, striking refineries throughout European Russia.
The governor of the frontier province of Belgorod, under near-constant attack in recent months, said five people, including a child, had been injured in a drone strike on a car traveling near the Ukrainian border.