(Bloomberg) -- Drones attacked a small oil refinery about 100 miles (161 kilometers) from Moscow, in the second apparent Ukrainian strike on Russian crude-processing facilities in two days.

The drones caused a fire at four fuel-storage tanks on the site of the refinery in Russia’s Kaluga region, RIA reported on Friday morning, citing emergency services. The blaze was extinguished around 7.30am local time, with no casualties, based on preliminary data, the Kaluga regional governor Vladislav Shapsha said on his Telegram account.

The Kaluga refinery, which had already attacked by Ukrainian drones in mid-March, has a nameplate capacity of 1.2 million tons of oil per year, or about 25,000 barrels a day, according to its website. That’s a tiny proportion of the 5.24 million barrels a day Russia’s downstream oil industry processed an average through most of April, according to data seen by Bloomberg.

It’s the second Ukrainian drone strike on Russian crude-processing facilities over the past two days. On Thursday, Gazprom PJSC’s Salavat Neftekhim petrochemical and oil-refining plant, located some 1,500 km (930 miles) from Moscow, was attacked causing a fire at the facility’s pumping station, according to Interfax.

Oil refining, one of Russia’s most important industries, has been a target of Ukrainian drone attacks since late January, as Kyiv seeks to curb fuel supplies to the front line and cut the flow of petrodollars to the Kremlin’s coffers. The attacks targeted some of Russia’s key refineries, initially causing partial or complete shutdowns. 

Lately, anti-drone systems have given the nation’s refiners time to regroup, deploy spare capacities and start repairs at the affected units. Of the facilities hit, only Rosneft PJSC’s Tuapse facility remained completely offline as of end-April, according to industry data seen by Bloomberg. 

Russian oil-processing plants have entered seasonal maintenance, which, in the absence of new successful Ukrainian drone attacks, is set to have a larger impact on the nation’s refinery runs than emergency repairs that followed previous strikes.

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