Ukraine has escalated its long-range drone campaign against Russia's energy infrastructure, striking deep into Tatarstan and killing at least 13 people, including a child. The attack, which targeted the oil hub of Nizhnekamsk roughly 800 kilometers east of Moscow, marks one of Kyiv's most ambitious and deadly strikes on Russian soil to date. Main Developments Monday's assault wounded at least 39 others, according to regional authorities, who declared a day of mourning in Tatarstan. Regional head Rustam Minnikhanov condemned the strike as "barbaric," asserting that civilian infrastructure was deliberately targeted. Russia's defence ministry reported intercepting more than 450 Ukrainian drones overnight, underscoring the scale of the coordinated offensive. Ukraine's military confirmed it successfully hit an oil facility in Nizhnekamsk, a city that hosts one of the country's largest and most advanced refineries. Read also: Western Europe Logs Hottest June-July on Record Svetlana Petrenko, spokesperson for Russia's Investigative Committee, confirmed a child was among the dead. Kyiv, she said, struck industrial facilities and civilians "who had no connection" to the military, prompting Moscow to open a criminal investigation into what it labels a "terrorist attack." In a parallel development, at least five people were killed in Ukraine's eastern Kharkiv region during what officials described as a "massive artillery attack" by Russian forces on a residential area in the Chuhuiv district. The regional prosecutor's office said investigations into potential war crimes are underway. Background The Nizhnekamsk strike follows a series of Ukrainian drone attacks on the same industrial zone in June and July, according to Al Jazeera's Yulia Shapovalova, reporting from Moscow. These raids are part of a broader strategy to cripple Russia's war economy by targeting fuel production and military logistics. Ukrainian President Volodymyr Zelenskyy signaled on Sunday that attacks on Russian oil refineries would continue, asserting that Moscow is "beginning to feel" the consequences. His remarks came amid ongoing exchanges of heavy strikes, with both sides intensifying their aerial campaigns. Why It Matters This attack demonstrates Ukraine's growing capability to strike deep into Russian territory, challenging the assumption that key economic assets are beyond reach. Nizhnekamsk's refinery is vital to Russia's oil exports, and repeated hits could disrupt fuel supplies and revenue. The civilian toll, including a child, raises the stakes for both sides. Russia's characterization of the strike as terrorism could prompt a harsher military response, while Ukraine frames its attacks as legitimate blows to wartime infrastructure. The international community watches closely as the conflict enters a new phase of long-range warfare. What's Next Zelenskyy has vowed to secure new air defence packages in the coming days and plans to speak with mediators this week to advance peace efforts. Moscow, meanwhile, has launched a criminal probe into the attack, signaling a potential escalation in its legal and military posture. The coming weeks will test whether Ukraine can sustain such large-scale drone operations and whether Russia can adapt its air defences. With both sides showing no sign of de-escalation, the prospect of further deep strikes looms large.