Four oil tanks at a large storage facility in the town of Klintsy in Russia's western Bryansk region caught fire on Friday after the military brought down a Ukrainian strike drone there, Alexander Bogomaz, the regional governor, said.
Aided by a specialised firefighting train, firefighters tackled what he said was a serious blaze at the facility controlled by oil major Rosneft (ROSN.MM). Nobody was hurt in the attack, he added.
"An aeroplane-style drone was brought down by the defence ministry using radio-electronic means. When the aerial target was destroyed, its munitions were dropped on the territory of the Klintsy oil depot," Bogomaz wrote on the Telegram messaging app.
He said air defence units had brought down two other Ukrainian drones on Friday over other parts of Bryansk, a region that borders Ukraine.
Both Russia and Ukraine have targeted each other's energy infrastructure in strikes designed to disrupt supply lines and logistics and to demoralise their opponent as they try to get the edge in a nearly two-year war that shows no sign of ending.
Bogomaz posted footage that showed firefighters directing water hoses at giant flames around the storage tanks, at least one of which looked to have been badly damaged, as thick smoke filled the air.
Andriy Yusov, a spokesperson for Ukraine's GUR military intelligence agency, neither confirmed nor denied Ukraine had been behind the attack, but said "such events regularly occur at the aggressor state's military facilities".
Yusov told national TV he expected the incident to complicate logistics for Russian troops, increasing Ukrainian forces' "room for manoeuvre".
Several Ukrainian media, citing sources in the security services, said the GUR, which did not immediately reply to a request for comment, was behind the strike.
A gunpowder factory in the Tambov region had also been targeted and the results of that strike effort were being clarified, the Ukrainska Pravda outlet quoted a source as saying.
Russia's TASS state news agency said the fire at the oil depot covered an area of around 1,000 square metres with other reports saying it was getting bigger.
Earlier on Friday, the Russian Defence Ministry said it had destroyed a Ukrainian drone in the skies over the Bryansk region, where authorities regularly report drone attacks from Ukraine.
A Russian-appointed official said on Thursday Ukraine had tried and failed to target a Russian Baltic Sea oil terminal with a drone, in what appeared to be a rare attempt to strike a facility in St Petersburg.
A Ukrainian government minister was quoted by the Interfax-Ukraine news agency on Thursday as saying that Ukraine had hit targets in St Petersburg using a domestically produced drone that flew 1,250 km (775 miles).
Reuters could not independently verify the statements.