Ukrainian attack on Russian oil refinery (Representative image)Ukraine launched one of its largest drone attacks on Russia overnight, setting fire to a major oil refinery in the country's south and killing at least two people, Russian authorities said on Sunday.Kyiv has significantly intensified its long-range strikes on Russian energy infrastructure and military-industrial facilities in recent months, aiming to disrupt Moscow's war effort and increase pressure on the Kremlin as the conflict enters its fifth year.Ukrainian President Volodymyr Zelenskyy said the attacks had targeted key Russian energy assets. "Tonight, our 'long-range sanctions' reached two oil refineries in Russia," Zelenskyy wrote on Telegram. "Each (strike) means a reduction in the resources that fuel the Russian war machine, and another step toward peace," he added.Major refinery in southern Russia hitRussian authorities said debris from intercepted Ukrainian drones sparked a fire at the Slavyansk oil refinery in Slavyansk-na-Kubani, in the Krasnodar region east of occupied Crimea, the Associated Press reported.According to regional governor Veniamin Kondratyev, one person was killed in Slavyansk and another was injured in a nearby village after debris from downed drones fell in the area.The Slavyansk refinery is among southern Russia's largest oil-processing facilities, handling nearly four million tonnes of crude oil annually. It is also a major supplier of petroleum products, including fuel oil, naphtha and marine fuel, exported through Russian Black Sea ports.Images and videos circulating on Russian social media showed thick plumes of smoke rising from what users identified as the refinery site, although the visuals could not be independently verified.Another refinery reportedly targetedZelenskyy also claimed that Ukrainian forces had struck another oil refinery in Russia's Yaroslavl region, around 700 kilometres from the Ukrainian border.Russian authorities did not immediately confirm a strike on the Yaroslavl refinery. However, regional governor Mikhail Evraev said several roads connecting Moscow and Yaroslavl had been temporarily closed due to "an enemy attack by Ukrainian drones."Russia's civil aviation authority also temporarily suspended operations at Yaroslavl airport and several airports in southern and western Russia. Russia's defence ministry said its air defence systems had destroyed 213 Ukrainian drones overnight over Russian territory, occupied Crimea, and the Black and Azov seas.Meanwhile, Ukraine's air force said Russia launched 142 long-range drones and eight missiles against Ukrainian targets overnight. Ukrainian air defences intercepted 125 drones and seven missiles, according to the forces.