A long-range drone operated by Ukraine's State Security Service (SBU) attacked an oil refinery, Gazprom Neftekhim Salavat, in Russia's Republic of Bashkortostan on May 9, an SBU source told the Kyiv Independent.
For the first time since the start of the full-scale invasion, Ukraine attacked facilities in Bashkortostan, some 1,500 kilometers from the country's border, according to the source.
In April, Ukraine hit production facilities in Russia's Tatarstan Republic, 1,300 kilometers away from the state border.
Gazprom Naftokhim Salavat is one of the largest oil refining and petrochemical production complexes in Russia. It specializes in the production of gasoline, diesel fuel, and other types of petroleum products.
The drone attack damaged an oil catalytic cracking unit of the refinery.
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"The SBU once again proved that it has powerful technological solutions that help deliver painful strikes to the enemy," the source said.
"It means that Russian refineries and oil depots operating for the military cannot feel safe even deep inside (Russia)."
Ukraine's State Security Service (SBU) earlier on the same day hit two oil depotsin Russia's Krasnodar Krai, according to a source interviewed by the Kyiv Independent.
The oil depots damaged in the attack are reportedly transshipment points for fuel supplies for Russian forces based in occupied Crimea.
Ukrainian forces have launched a series of drone strikes aimed at damaging Russia's oil industry this spring. A large-scale attack against Russian energy infrastructure on April 20 reportedly started a fire at a fuel storage tank in Smolensk Oblast.
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: How Ukraine hit a Russian drone factory 1,300 kilometers away