New Delhi, Sept. 15 -- Ukrainian drones have struck one of Russia's largest oil refineries, sparking a fire, Russian officials and Ukraine's military said Sunday.

The overnight strike on the Kirishi refinery, in Russia's northwestern Leningrad region, follows weeks of Ukrainian attacks on Russian oil infrastructure that Kyiv says fuels Moscow's war effort.

The facility, operated by Russian company Surgutneftegas, produces close to 17.7 million metric tons per year (355,000 barrels per day) of crude, and is one of Russia's top three by output.

More than three years since Russia's full-scale invasion of Ukraine, drones continue to be a key weapon for both sides. Multiple Russian drones crossed into Poland on Wednesday, prompting NATO to ...