The Ukrainian military said Monday that its drones struck Russia’s largest oil refinery in the western Siberian region of Omsk, marking one of the deepest attacks on Russian territory since the full-scale invasion of Ukraine.

The Gazprom Neft-operated refinery is located on the northern outskirts of the city of Omsk, around 2,500 kilometers (1,550 miles) from the border with Ukraine. NASA satellites recorded multiple fire hotspots at the facility on Monday evening.

“An impact with subsequent fire was recorded on the territory [of the refinery]. The extent of the damage is being verified,” Ukraine’s General Staff said in a statement on Facebook. “This is the last of the 11 largest gasoline producers in Russia that have been hit.”

Omsk region Governor Vitaly Khotsenko confirmed that “several drones” had broken through layers of Russian air defense and attacked the refinery. Without specifying what, if anything, was damaged, Khotsenko said that emergency services were dispatched to the facility.

The strikes mark the first time the Omsk region has come under a Ukrainian drone attack since the 2022 invasion.