KYIV, Ukraine (AP) — Ukraine kept up its heavy drone assault on Russia, setting fire to a major oil refinery in the south and killing at least two people, Russian authorities said Sunday.

Ukraine has markedly stepped up its long-range attacks on Russian military industries and energy facilities in recent months, aiming to cut Moscow’s revenue for its invasion — now in its fifth year — and make Russians feel the consequences.

The campaign has choked Russian fuel supplies and military deliveries. According to Western analysts, it has also slowed Moscow’s efforts on the battlefield, heaping pressure on the Kremlin to come to the negotiating table.

“Our ‘long-range sanctions’ reached two oil refineries in Russia,” Ukrainian President Volodymyr Zelenskyy wrote on the Telegram messaging app on Sunday. “Each (strike) means a reduction in the resources that fuel the Russian war machine, and another step toward peace.”

Debris from downed Ukrainian drones sparked a blaze at the refinery in Slavyansk-na-Kubani, a town in Russia's Krasnodar region, east of occupied Crimea, according to Gov. Veniamin Kondratyev. The falling debris killed one person in Slavyansk and wounded another in a nearby village, according to regional authorities.

The Slavyansk site is one of southern Russia’s major refineries, processing close to 4 million tons of crude per year, according to its operator’s website. It is also a key source of petroleum products intended for export through Russia’s Black Sea ports, including fuel oil, naphtha and marine fuel.

Photos and videos circulating on Russian social media showed a thick cloud of smoke over what users said was the Slavyansk facility. The Associated Press was not immediately able to verify the images.

Zelenskyy also claimed that a second Russian refinery, in the Yaroslavl region around 700 kilometers (435 miles) from the Ukrainian border, was hit during the nighttime strikes.

There were no immediate reports from Russian authorities about the Ukrainian strike on the Yaroslavl refinery. Local Gov. Mikhail Evraev reported on Sunday morning that some roads between Moscow and the region's capital, Yaroslavl, were temporarily closed due to “an enemy attack by Ukrainian drones”.

Yaroslavl's airport also briefly closed overnight, along with others in southern and western Russia, according to the country's civil aviation agency.

For months, Ukraine has been stepping up attacks on energy facilities deep inside Russia, arguing the sector both funds and directly fuels the Kremlin's invasion. Despite a raft of Western sanctions, Moscow remains among the world's top exporters of oil and natural gas.

More recently, Ukraine has attempted to choke off fuel deliveries to Crimea, the Black Sea peninsula Moscow illegally annexed from it in early 2014. Last weekend, Kremlin-installed officials in Crimea suspended gasoline sales to civilians, after Kyiv's targeting of supply routes triggered the worst energy crisis there since the annexation.

Civilian fuel sales were also being restricted in Russia’s Irkutsk region in Siberia, thousands of kilometers (miles) from the Ukrainian border, local Gov. Igor Kobzev announced on Sunday.

Drivers will be barred from buying more than 50 litres of fuel per vehicle per day at state-run Rosneft gas stations in the province, Kobzev said, while “other gas stations may set lower limits.”

At least two private gas station networks in Siberia — KreisNeft in the Irkutsk region and Elke Auto in the Tomsk region further west — said earlier this month that they were limiting fuel sales due to supply disruptions.

Elsewhere, Ukrainian drone strikes killed one person and injured another in Russia’s border region of Belgorod, its acting Gov. Alexander Shuvayev reported on Sunday.

Russia’s Defense Ministry said its forces shot down 213 Ukrainian drones during the night, including over Russia, occupied Crimea and the Black and Azov seas.

Meanwhile, Russia attacked Ukraine with 142 long-range strike drones and eight missiles overnight, according to the Ukrainian air force. Of those, 125 drones and seven missiles were struck down, the air force said.

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