Regional governor Rustam Minnikhanov said the drone was destroyed but falling debris ignited a fire and struck a vehicle manufacturing plant in the Yelabuga district, about 1200km from the frontline.
Ukraine's military said it had hit a Russian drone factory in the city of Yelabuga.
The Ukrainian General Staff did not say how it had struck the target.
It said on the Telegram platform that the facility was used to produce, test and launch drones at Ukraine, in particular against energy and civil infrastructure.
Russia's defence ministry said it shot down six Ukrainian drones overnight.
Russia launched 183 drones and decoys, along with 11 missiles, at Ukraine overnight, according to the Ukrainian air force, which said its air defences destroyed 111 drones and eight missiles while another 48 drones were jammed.
Officials in the Poltava region said the overnight attack damaged energy and agricultural infrastructure but there were no casualties.
Continuing a renewed battlefield push along eastern and northeastern parts of the more than 600-mile front line, the Russian Defense Ministry said on Sunday that its troops captured another village in the Donetsk region, Malynivka.
The Ukrainian military had no immediate comment on the Russian claim.
The continued attacks came a day after Russian President Vladimir Putin and US President Donald Trump held a lengthy call, during which Trump said that he pressed Putin to end the war in Ukraine.
In other developments, Russia repatriated more bodies of fallen soldiers in line with an agreement reached during peace talks in Istanbul between Russian and Ukrainian delegations, Russian officials said on Sunday, cited by Russian state media.
The officials said Ukraine did not return any bodies to Russia on Sunday.
Ukraine's Co-ordination Headquarters for the Treatment of Prisoners of War confirmed in a statement that Russia returned 1200 bodies.
The agreement to exchange prisoners of war and the bodies of fallen soldiers was the only tangible outcome of the June 2 Istanbul talks.
The first round of the staggered exchanges took place on Monday.
with Reuters
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