KYIV, Ukraine (AP) — Ukrainian drones struck a major refinery deep inside Russia, military officials said Thursday, the fourth in three days in Kyiv’s ongoing campaign to choke Moscow’s vital oil sector.Russia is one of the world’s biggest energy producers, with oil providing an economic mainstay as its military tries to push deeper into Ukraine in a slow and costly advance more than four years after Moscow launched its full-scale invasion.The attacks have dented Russia’s refining capacity, causing shortages at gas stations. Kyiv officials say the onslaught is meant to compel Russian President Vladimir Putin to seek a peace deal, but there’s no sign that strategy is working.

The targeted refinery is one of Russia’s biggest Ukraine’s General Staff said its forces struck the Gazprom Neftekhim Salavat oil refining and petrochemical complex in Russia’s republic of Bashkortostan overnight, causing a fire at the facility.The complex, located southeast of Moscow about 1,300 kilometers (800 miles) from Ukraine’s border, is one of Russia’s largest such facilities, the General Staff said in a Telegram post. The plant processes up to 74 million barrels of oil annually, producing gasoline, diesel fuel and other products, it said.Bashkortostan Gov. Radiy Khabirov said only that a drone attack wounded two civilians and started a fire in an industrial zone of Salavat.