(Bloomberg) -- Four refineries in southern Russia were targeted overnight, with one suffering damage, in one of the largest swarm attacks from drones since the war in Ukraine began.

Seventy drones were intercepted and destroyed over Crimea and the Black Sea and 43 over the Krasnodar region, the Russian Defense Ministry said on Telegram, without saying how many drones took part in the attack. The Afipsky, Ilsky, Krasnodar and Astrakhan refineries were attacked, Ukraine’s General Staff said later in a Facebook post. 

In the Seversky district of the Krasnodar region, where the Afipsky and Ilsky refineries are located, “administrative buildings were damaged on the territory of an oil refinery” as a result of the attack, local governor Veniamin Kondratyev said on Telegram. Interfax earlier reported that a fire affecting area of ​​50 square meters (538 square feet) was extinguished by morning, with two people injured.

The Ilsky, Afipsky, Krasnodar and Astrakhan refineries didn’t respond immediately to Bloomberg News requests for comment on the impact of the attacks.

Oil refining is one of Russia’s most important industries and has been a target of Ukrainian drone attacks since late January. More than two years after being invaded by its neighbor, Kyiv is attempting to curb Moscow’s ability to finance the aggression and disrupt fuel supplies to front-line troops.

In the past several weeks, Ukrainian drone attacks damaged at least two other refineries in southern Russia, including Rosneft’s large Tuapse facility on the Black Sea on May 17. Before that attack, Russia’s crude-processing rates had been increasing, averaging 5.45 million barrels a day in the first 15 days of May, according to the latest available data. 

Refineries are being repaired at a fast pace after the drone attacks, Deputy Prime Minister Alexander Novak said on May 22. Russia has been improving its mechanisms and technology to protect energy facilities, he said.

Even amid the usual seasonal refinery maintenance, the situation on Russia’s domestic fuel market “is absolutely stable” with facilities producing more diesel and gasoline than a year ago, Novak said earlier this month. 

Following an initial flurry of attacks on refineries at the start of the year, the Russian government restricted gasoline exports from March 1 for six months. The ban was temporarily lifted from May 20 to the end of June as domestic fuel supplies became more plentiful, and the government is now considering allowing overseas shipments to continue in July, according to the people with knowledge of the matter. 

Both Ilsky and Afipsky have previously been targets for Ukrainian drone attack. The Ilsky refinery processed more than 114,000 barrels a day of crude in the first 15 days of May, or some 2.1% of nation’s total refinery runs, according to a person with knowledge of the matter. The Afipsky facility churned through over 146,000 barrels a day in the same period, or 2.7% of Russia’s crude processing volumes, the person said. 

The Defense Ministry also said Russian war planes destroyed six naval drones in the northwestern part of the Black Sea overnight. 

(Updates with details throughout.)

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