Ukraine's military intelligence agency (HUR) was behind the May 10 attack on the oil refinery in Russia's Kaluga Oblast, a source in the agency confirmed to the Kyiv Independent.
Kaluga OblastGovernor Vladyslav Shapsha claimed earlier in the day that a falling drone caused a fire in the Dzerzhinsky district overnight.
The governor did not specify the facility being attacked, but locals reported the fire at the Pervyy Zavod plant, the largest petrochemical enterprise in Kaluga Oblast, according to the Russian Telegram channel Mash.
The oil refinery, located nearly 350 kilometers (around 220 miles) from Ukraine's border, specializes in the processing of commodity oil and gas condensate.
Moscow Mayor Sergey Sobyanin claimed later that Russian air defenses downed a drone heading toward the Russian capital.
No casualties or damage were reported by the mayor.
The source confirmed for the Kyiv Independent that Ukraine's military intelligence agency was involved in the attack. The strike reportedly was carried out with kamikaze drones.
Ukrainian forces previously struck the Pervyy Zavod plant on March 15, 2024.
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Ukrainian forces have launched a series of drone strikes aimed at damaging Russia's oil industry this spring.
On May 9, the Security Service of Ukraine (SBU) attacked an oil refinery, Gazprom Neftekhim Salavat, in the Republic of Bashkortostan, and two oil depots in Krasnodar Krai, according to a source interviewed by the Kyiv Independent.
Strikes against Russian energy targets have prompted criticism from U.S. officials, who have made it clear that Washington does not support Ukraine's attacks on oil refineries, citing fears that it could threaten the global energy market.
In response, President Volodymyr Zelensky said that Kyiv has the right to use its own weapons with retaliatory strikes on Russian oil refineries.
Read also: Reuters: Russia faces difficulties repairing oil refineries due to US sanctions