Russian President Vladimir Putin, center, chairs a meeting on domestic fuel supplies at the Kremlin in Moscow, Sunday. (Gavriil Grigorov/Sputnik, Kremlin Pool Photo via AP)

KYIV, Ukraine (AP) — Ukraine kept up its heavy drone assault on Russia, setting fire to a major oil refinery in the south, as President Vladimir Putin acknowledged for the first time on Sunday that the country was facing a “certain deficit” of fuel and vowed to strengthen protection of oil facilities and boost fuel output.

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.

“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.”

The campaign has choked Russian fuel supplies, causing widespread shortages and long lines at gas stations across the country and prompting authorities in many regions to introduce fuel rationing. 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.

Speaking to a Russian state TV reporter, Putin described the Ukrainian attacks on oil refineries as an attempt to “cause a split in Russian society and force Russia to halt, even if only briefly, the advance of our troops along the line of contact, and create conditions for launching a negotiation process on terms advantageous to our adversary.”

“We will not give them that chance,” Putin said, adding that “strikes on our infrastructure, wherever they are directed, have absolutely no effect on the situation at the front, on the line of contact.”

He said for the first time that Ukraine has proposed a halt on deep strikes, arguing that Kyiv made the offer because Russian strikes deep into Ukrainian territory are more powerful and devastating.

The Russian leader added that Kyiv also offered to limit the fighting to the four regions that Russia annexed but never fully captured – Donetsk, Luhansk, Kherson and Zaporizhzhia. He rejected the proposal, arguing it would allow Ukraine to relocate its forces that are fighting Russian troops in other areas to let them focus on fending off the Russian attacks in the four southeastern regions.

Meanwhile, 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 regional Governor Veniamin Kondratyev. The falling debris killed one person in Slavyansk and wounded another in a nearby village, local authorities said.

The facility 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.

Zelenskyy also claimed that another Russian refinery, in the Yaroslavl region around 435 miles from the Ukrainian border, was hit during the nighttime strikes.